Wavelength multiplexing in waveguides

ABSTRACT

A stacked waveguide assembly can have multiple waveguide stacks. Each waveguide stack can include a plurality of waveguides, where a first waveguide stack may be associated with a first subcolor of each of three different colors, and a second waveguide stack may be associated with a second subcolor of each of the three different colors. For example, the first stack of waveguides can incouple blue, green, and red light at 440 nm, 520 nm, and 650 nm, respectively. The second stack of waveguides can incouple blue, green, and red light at 450 nm, 530 nm, and 660 nm, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119(e)to U.S. Provisional Application No. 62/335,223, filed on May 12, 2016,entitled “DISTRIBUTED LIGHT MANIPULATION OVER IMAGING WAVEGUIDE,” and toU.S. Provisional Application No. 62/335,232, filed on May 12, 2016,entitled “WAVELENGTH MULTIPLEXING IN WAVEGUIDES,” both of which arehereby incorporated by reference herein in their entirety.

FIELD

The present disclosure relates to virtual reality and augmented realityimaging and visualization systems and more particularly to distributinglight to different regions of a waveguide.

BACKGROUND

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, wherein digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves presentation of digital or virtual image informationwithout transparency to other actual real-world visual input; anaugmented reality, or “AR”, scenario typically involves presentation ofdigital or virtual image information as an augmentation to visualizationof the actual world around the user. For example, referring to FIG. 1,an augmented reality scene 1000 is depicted wherein a user of an ARtechnology sees a real-world park-like setting 1100 featuring people,trees, buildings in the background, and a concrete platform 1120. Inaddition to these items, the user of the AR technology also perceivesthat he “sees” a robot statue 1110 standing upon the real-world platform1120, and a cartoon-like avatar character 1130 flying by which seems tobe a personification of a bumble bee, even though these elements do notexist in the real world. As it turns out, the human visual perceptionsystem is very complex, and producing a VR or AR technology thatfacilitates a comfortable, natural-feeling, rich presentation of virtualimage elements amongst other virtual or real-world imagery elements ischallenging. Systems and methods disclosed herein address variouschallenges related to VR and AR technology.

SUMMARY

Examples of waveguides and stacked waveguide assemblies that can be usedin wearable display systems are described herein.

An embodiment of a waveguide comprises an incoupling optical element,configured to incouple light at a first wavelength and to couple lightout of the waveguide that is not at the first wavelength. The waveguidefurther comprises a wavelength selective region, where the wavelengthselective region is configured to receive the incoupled light from theincoupling optical element and to propagate the incoupled light to alight distributing element. The wavelength selective region can beconfigured to attenuate the incoupled light not at the first wavelengthrelative to incoupled light at the first wavelength. The lightdistributing element can be configured to couple the incoupled light atthe first wavelength out of the wavelength selective region. Thewaveguide also comprises an outcoupling optical element configured toreceive the incoupled light at the first wavelength from the lightdistributing element and to couple the incoupled light at the firstwavelength out of the waveguide.

An embodiment of a stacked waveguide assembly comprises a firstwaveguide, which comprises a first incoupling optical element that isconfigured to incouple light at a first wavelength and to couple lightnot at the first wavelength out of the first waveguide. The firstwaveguide further comprises a first wavelength selective region that isconfigured to receive incoupled light from the first incoupling opticalelement and to propagate the incoupled light to a first lightdistributing element. The first wavelength selective region isconfigured to attenuate the incoupled light not at the first wavelengthrelative to incoupled light at the first wavelength and to couple theincoupled light at the first wavelength out of the first wavelengthselective region. The first waveguide also comprises a first outcouplingoptical element that is configured to receive the incoupled light at thefirst wavelength from the first light distributing element and to couplethe incoupled light not at the first wavelength out of the firstwaveguide.

The embodiment of the stacked waveguide assembly further comprises asecond waveguide, which comprises a second incoupling optical elementthat is configured to receive incident light at a second wavelengthdifferent from the first wavelength from the first incoupling opticalelement, to couple incident light not at the second wavelength out ofthe second waveguide, and to incouple the incident light at the secondwavelength. The second waveguide further comprises a second wavelengthselective region that is configured to receive incoupled light from thesecond incoupling optical element and to propagate the incoupled lightto a second light distributing element. The second wavelength selectiveregion is configured to attenuate the incoupled light not at the secondwavelength relative to incoupled light at the second wavelength. Thesecond light distributing element is configured to couple the incoupledlight at the second wavelength out of the second wavelength selectiveregion. The second waveguide also comprises a second outcoupling opticalelement that is configured to receive the incoupled light at the secondwavelength from the second light distributing element and to couple theincoupled light not at the second wavelength out of the secondwaveguide.

An embodiment of a method of displaying an optical image comprisesincoupling light having a first wavelength and a second wavelengthdifferent from the first wavelength into a stacked waveguide assembly.The stacked waveguide assembly comprises a first waveguide and a secondwaveguide, wherein the first waveguide comprises a first layer of awavelength selective region and a first layer of an outcoupling opticalelement. The second waveguide comprises a second layer of the wavelengthselective region and a second layer of the outcoupling optical element.The method further comprises selectively attenuating the incoupled lightat the second wavelength relative to the first wavelength in the firstlayer of the wavelength selective region and selectively attenuating theincoupled light at the first wavelength relative to the first wavelengthin the second layer of the wavelength selective region. The methodfurther comprises coupling the incoupled light at the first wavelengthto the first layer of the outcoupling optical element and coupling theincoupled light at the first wavelength to the second layer of theoutcoupling optical element. The method also comprises coupling theincoupled light at the first wavelength and the second wavelength out ofthe stacked waveguide assembly.

Another embodiment of a method of displaying an optical image comprisesincoupling light having a first wavelength and a second wavelengthdifferent from the first wavelength into a waveguide and selectivelyattenuating the incoupled light at the second wavelength relative to thefirst wavelength in a first layer of a wavelength selective region. Themethod further comprises selectively attenuating the incoupled light atthe first wavelength relative to the second wavelength in a second layerof the wavelength selective region and coupling the incoupled light atthe first wavelength from a first light distributing element to a firstlayer of an outcoupling optical element. The method further comprisescoupling the incoupled light at the second wavelength from a secondlight distributing element to a second layer of the outcoupling opticalelement and coupling the incoupled light at the first wavelength andsecond wavelength out of the outcoupling optical element.

Details of one or more implementations of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages will becomeapparent from the description, the drawings, and the claims. Neitherthis summary nor the following detailed description purports to defineor limit the scope of the inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustration of an augmented reality scenario withcertain virtual reality objects, and certain actual reality objectsviewed by a person.

FIG. 2 schematically illustrates an example of a wearable displaysystem.

FIG. 3 schematically illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes.

FIG. 4 schematically illustrates an example of a waveguide stack foroutputting image information to a user.

FIG. 5 shows example exit beams that may be outputted by a waveguide.

FIG. 6 is a schematic diagram showing an optical system including awaveguide apparatus, an optical coupler subsystem to optically couplelight to or from the waveguide apparatus, and a control subsystem, usedin the generation of a multi-focal volumetric display, image, or lightfield.

FIG. 7A is a top view that schematically illustrates an example of adisplay including a waveguide that comprises an incoupling opticalelement, a light distributing element, and an outcoupling opticalelement.

FIG. 7B is a cross-sectional view of the display depicted in FIG. 7Aalong the axis A-A′.

FIG. 8 is a top view that schematically illustrates an example of adisplay including a waveguide, an incoupling optical element, a lightdistributing element including a wavelength selective region, and anoutcoupling optical element.

FIG. 9 illustrates a perspective view of an example a stacked waveguideassembly.

FIG. 10A is a side view that schematically illustrates an exampledisplay where two waveguides include color filters.

FIG. 10B is a side view that schematically illustrates an exampledisplay where two waveguides include distributed switch materials.

FIG. 11 is a side view that schematically illustrates an examplewaveguide with multiple filter regions.

FIG. 12 illustrates an example of a series of subcolors within a color.

FIG. 13 schematically illustrates a side view of an example stackedwaveguide assembly.

FIG. 14 schematically illustrates a side view of an example stackedwaveguide assembly with a preliminary light filter system.

FIG. 15A shows an example of the waveguide assembly of FIG. 13 withdistributed filters.

FIG. 15B shows an example of the waveguide assembly of FIG. 13 withdistributed switches.

FIG. 16 is a chromaticity diagram describing the hypothetical humanvisual response gamut at which colors are perceived.

Throughout the drawings, reference numbers may be re-used to indicatecorrespondence between referenced elements. The drawings are provided toillustrate example embodiments described herein and are not intended tolimit the scope of the disclosure.

DETAILED DESCRIPTION Overview

In order for a three-dimensional (3D) display to produce a truesensation of depth, and more specifically, a simulated sensation ofsurface depth, it is desirable for each point in the display's visualfield to generate the accommodative response corresponding to itsvirtual depth. If the accommodative response to a display point does notcorrespond to the virtual depth of that point, as determined by thebinocular depth cues of convergence and stereopsis, the human eye mayexperience an accommodation conflict, resulting in unstable imaging,harmful eye strain, headaches, and, in the absence of accommodationinformation, almost a complete lack of surface depth.

VR and AR experiences can be provided by display systems having displaysin which images corresponding to a plurality of depth planes areprovided to a viewer. The images may be different for each depth plane(e.g., provide slightly different presentations of a scene or object)and may be separately focused by the viewer's eyes, thereby helping toprovide the user with depth cues based on the accommodation of the eyerequired to bring into focus different image features for the scenelocated on different depth plane and/or based on observing differentimage features on different depth planes being out of focus. Asdiscussed elsewhere herein, such depth cues provide credible perceptionsof depth.

FIG. 2 illustrates an example of wearable display system 100. Thedisplay system 100 includes a display 62, and various mechanical andelectronic modules and systems to support the functioning of display 62.The display 62 may be coupled to a frame 64, which is wearable by adisplay system user, wearer, or viewer 60 and which is configured toposition the display 62 in front of the eyes of the user 60. In someembodiments, a speaker 66 is coupled to the frame 64 and positionedadjacent the ear canal of the user (in some embodiments, anotherspeaker, not shown, is positioned adjacent the other ear canal of theuser to provide for stereo/shapeable sound control). The display 62 isoperatively coupled 68, such as by a wired lead or wirelessconnectivity, to a local data processing module 71 which may be mountedin a variety of configurations, such as fixedly attached to the frame64, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 60 (e.g., in abackpack-style configuration, in a belt-coupling style configuration).

The local processing and data module 71 may comprise a hardwareprocessor, as well as digital memory, such as non-volatile memory (e.g.,flash memory), both of which may be utilized to assist in theprocessing, caching, and storage of data. The data may include data a)captured from sensors (which may be, e.g., operatively coupled to theframe 64 or otherwise attached to the user 60), such as image capturedevices (e.g., cameras), microphones, inertial measurement units,accelerometers, compasses, global positioning system (GPS) units, radiodevices, and/or gyroscopes; and/or b) acquired and/or processed usingremote processing module 72 and/or remote data repository 74, possiblyfor passage to the display 62 after such processing or retrieval. Thelocal processing and data module 71 may be operatively coupled bycommunication links 76 and/or 78, such as via wired or wirelesscommunication links, to the remote processing module 72 and/or remotedata repository 74 such that these remote modules are available asresources to the local processing and data module 71. In addition,remote processing module 72 and remote data repository 74 may beoperatively coupled to each other.

In some embodiments, the remote processing module 72 may comprise one ormore processors configured to analyze and process data and/or imageinformation. In some embodiments, the remote data repository 74 maycomprise a digital data storage facility, which may be available throughthe internet or other networking configuration in a “cloud” resourceconfiguration. In some embodiments, all data is stored and allcomputations are performed in the local processing and data module,allowing fully autonomous use from a remote module.

The human visual system is complicated and providing a realisticperception of depth is challenging. Without being limited by theory, itis believed that viewers of an object may perceive the object as beingthree-dimensional due to a combination of vergence and accommodation.Vergence movements (e.g., rotational movements of the pupils toward oraway from each other to converge the lines of sight of the eyes tofixate upon an object) of the two eyes relative to each other areclosely associated with focusing (or “accommodation”) of the lenses ofthe eyes. Under normal conditions, changing the focus of the lenses ofthe eyes, or accommodating the eyes, to change focus from one object toanother object at a different distance will automatically cause amatching change in vergence to the same distance, under a relationshipknown as the “accommodation-vergence reflex.” Likewise, a change invergence will trigger a matching change in accommodation, under normalconditions. Display systems that provide a better match betweenaccommodation and vergence may form more realistic or comfortablesimulations of three-dimensional imagery.

FIG. 3 illustrates aspects of an approach for simulatingthree-dimensional imagery using multiple depth planes. With reference toFIG. 3, objects at various distances from eyes 302 and 304 on the z-axisare accommodated by the eyes 302 and 304 so that those objects are infocus. The eyes 302 and 304 assume particular accommodated states tobring into focus objects at different distances along the z-axis.Consequently, a particular accommodated state may be said to beassociated with a particular one of depth planes 306, with has anassociated focal distance, such that objects or parts of objects in aparticular depth plane are in focus when the eye is in the accommodatedstate for that depth plane. In some embodiments, three-dimensionalimagery may be simulated by providing different presentations of animage for each of the eyes 302 and 304, and also by providing differentpresentations of the image corresponding to each of the depth planes.While shown as being separate for clarity of illustration, the fields ofview of the eyes 302 and 304 may overlap, for example, as distance alongthe z-axis increases. In addition, while shown as flat for ease ofillustration, the contours of a depth plane may be curved in physicalspace, such that all features in a depth plane are in focus with the eyein a particular accommodated state. Without being limited by theory, itis believed that the human eye typically can interpret a finite numberof depth planes to provide depth perception. Consequently, a highlybelievable simulation of perceived depth may be achieved by providing,to the eye, different presentations of an image corresponding to each ofthese limited number of depth planes.

Waveguide Stack Assembly

FIG. 4 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 100 includes a stack ofwaveguides, or stacked waveguide assembly, 178 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 182, 184, 186, 188, 190. In some embodiments, the displaysystem 100 shown in FIG. 4 may be used in the wearable display system100 shown in FIG. 2, with FIG. 4 schematically showing some parts ofthat system 100 in greater detail. For example, in some embodiments, thewaveguide assembly 178 may be integrated into the display 62 of FIG. 2.

With continued reference to FIG. 4, the waveguide assembly 178 may alsoinclude a plurality of features 198, 196, 194, 192 between thewaveguides. In some embodiments, the features 198, 196, 194, 192 may belenses. The waveguides 182, 184, 186, 188, 190 and/or the plurality oflenses 198, 196, 194, 192 may be configured to send image information tothe eye with various levels of wavefront curvature or light raydivergence. Each waveguide level may be associated with a particulardepth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 200, 202,204, 206, 208 may be utilized to inject image information into thewaveguides 182, 184, 186, 188, 190, each of which may be configured todistribute incoming light across each respective waveguide, for outputtoward the eye 304. Light exits an output surface of the image injectiondevices 200, 202, 204, 206, 208 and is injected into a correspondinginput edge of the waveguides 182, 184, 186, 188, 190. In someembodiments, a single beam of light (e.g., a collimated beam) is beinjected into each waveguide to output an entire field of clonedcollimated beams that are directed toward the eye 304 at particularangles (and amounts of divergence) corresponding to the depth planeassociated with a particular waveguide.

In some embodiments, the image injection devices 200, 202, 204, 206, 208are discrete displays that each produce image information for injectioninto a corresponding waveguide 182, 184, 186, 188, 190, respectively. Insome other embodiments, the image injection devices 200, 202, 204, 206,208 are the output ends of a single multiplexed display which may, e.g.,pipe image information via one or more optical conduits (such as fiberoptic cables) to each of the image injection devices 200, 202, 204, 206,208.

A controller 210 controls the operation of the stacked waveguideassembly 178 and the image injection devices 200, 202, 204, 206, 208. Insome embodiments, the controller 210 includes programming (e.g.,instructions in a non-transitory computer-readable medium) thatregulates the timing and provision of image information to thewaveguides 182, 184, 186, 188, 190. In some embodiments, the controlleris be a single integral device (e.g., a hardware processor), or adistributed system connected by wired or wireless communicationchannels. The controller 210 is part of the processing modules 71 or 72(illustrated in FIG. 2) in some embodiments.

The waveguides 182, 184, 186, 188, 190 may be configured to propagatelight within each respective waveguide by total internal reflection(TIR). The waveguides 182, 184, 186, 188, 190 may each be planar or haveanother shape (e.g., curved), with major top and bottom surfaces andedges extending between those major top and bottom surfaces. In theillustrated configuration, the waveguides 182, 184, 186, 188, 190 mayeach include light extracting optical elements 282, 284, 286, 288, 290that are configured to extract light out of a waveguide by redirectingthe light, propagating within each respective waveguide, out of thewaveguide to output image information to the eye 304. Extracted lightmay also be referred to as outcoupled light, and light extractingoptical elements may also be referred to as outcoupling opticalelements. An extracted beam of light is outputted by the waveguide atlocations at which the light propagating in the waveguide strikes alight redirecting element. The light extracting optical elements 82,284, 286, 288, 290 may, for example, be reflective and/or diffractiveoptical features. While illustrated disposed at the bottom surfaces ofthe waveguides 182, 184, 186, 188, 190 for ease of description anddrawing clarity, in some embodiments, the light extracting opticalelements 282, 284, 286, 288, 290 are disposed at the top and/or bottomsurfaces, and/or may be disposed directly in the volume of thewaveguides 182, 184, 186, 188, 190. In some embodiments, the lightextracting optical elements 282, 284, 286, 288, 290 are formed in alayer of material that is attached to a transparent substrate to formthe waveguides 182, 184, 186, 188, 190. In some other embodiments, thewaveguides 182, 184, 186, 188, 190 are a monolithic piece of materialand the light extracting optical elements 282, 284, 286, 288, 290 may beformed on a surface and/or in the interior of that piece of material.

With continued reference to FIG. 4, as discussed herein, each waveguide182, 184, 186, 188, 190 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide182 nearest the eye may be configured to deliver collimated light, asinjected into such waveguide 182, to the eye 304. The collimated lightmay be representative of the optical infinity focal plane. The nextwaveguide up 184 may be configured to send out collimated light whichpasses through the first lens 192 (e.g., a negative lens) before it canreach the eye 304. First lens 192 may be configured to create a slightconvex wavefront curvature so that the eye/brain interprets light comingfrom that next waveguide up 184 as coming from a first focal planecloser inward toward the eye 304 from optical infinity. Similarly, thethird up waveguide 186 passes its output light through both the firstlens 192 and second lens 194 before reaching the eye 304. The combinedoptical power of the first and second lenses 192 and 194 may beconfigured to create another incremental amount of wavefront curvatureso that the eye/brain interprets light coming from the third waveguide186 as coming from a second focal plane that is even closer inwardtoward the person from optical infinity than was light from the nextwaveguide up 184.

The other waveguide layers (e.g., waveguides 188, 190) and lenses (e.g.,lenses 196, 198) are similarly configured, with the highest waveguide190 in the stack sending its output through all of the lenses between itand the eye for an aggregate focal power representative of the closestfocal plane to the person. To compensate for the stack of lenses 198,196, 194, 192 when viewing/interpreting light coming from the world 144on the other side of the stacked waveguide assembly 178, a compensatinglens layer 180 may be disposed at the top of the stack to compensate forthe aggregate power of the lens stack 198, 196, 194, 192 below. Such aconfiguration provides as many perceived focal planes as there areavailable waveguide/lens pairings. Both the light extracting opticalelements of the waveguides and the focusing aspects of the lenses may bestatic (e.g., not dynamic or electro-active). In some alternativeembodiments, either or both are dynamic using electro-active features.

With continued reference to FIG. 4, the light extracting opticalelements 282, 284, 286, 288, 290 may be configured to both redirectlight out of their respective waveguides and to output this light withthe appropriate amount of divergence or collimation for a particulardepth plane associated with the waveguide. As a result, waveguideshaving different associated depth planes may have differentconfigurations of light extracting optical elements, which output lightwith a different amount of divergence depending on the associated depthplane. In some embodiments, as discussed herein, the light extractingoptical elements 282, 284, 286, 288, 290 are volumetric or surfacefeatures, which may be configured to output light at specific angles.For example, the light extracting optical elements 282, 284, 286, 288,290 may be volume holograms, surface holograms, and/or diffractiongratings. Light extracting optical elements, such as diffractiongratings, are described in U.S. Patent Publication No. 2015/0178939,published Jun. 25, 2015, which is hereby incorporated by referenceherein in its entirety. In some embodiments, the features 198, 196, 194,192 are not lenses. Rather, they may simply be spacers (e.g., claddinglayers and/or structures for forming air gaps).

In some embodiments, the light extracting optical elements 282, 284,286, 288, 290 are diffractive features that form a diffraction pattern,or “diffractive optical element” (also referred to herein as a “DOE”).In some cases, the DOEs have a relatively low diffraction efficiency sothat only a portion of the light of the beam is deflected (e.g.,refracted, reflected, or diffracted) away toward the eye 304 with eachintersection of the DOE, while the rest continues to move through awaveguide via total internal reflection. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 304 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs are switchable between “on” statesin which they actively diffract, and “off” states in which they do notsignificantly diffract. For instance, a switchable DOE may comprise alayer of polymer dispersed liquid crystal, in which microdropletscomprise a diffraction pattern in a host medium, and the refractiveindex of the microdroplets can be switched to substantially match therefractive index of the host material (in which case the pattern doesnot appreciably diffract incident light) or the microdroplet can beswitched to an index that does not match that of the host medium (inwhich case the pattern actively diffracts incident light).

In some embodiments, the number and distribution of depth planes and/ordepth of field can be varied dynamically based on the pupil sizes and/ororientations of the eyes of the viewer. In some embodiments, a camera500 (e.g., a digital camera) can be used to capture images of the eye304 to determine the size and/or orientation of the pupil of the eye304. The camera 500 can be used to obtain images for use in determiningthe direction the wearer 60 is looking (e.g., eye pose) or for biometricidentification of the wearer (e.g., via iris identification). In someembodiments, the camera 500 is attached to the frame 64 (as illustratedin FIG. 2) and may be in electrical communication with the processingmodules 71 and/or 72, which may process image information from thecamera 500 to determine, e.g., the pupil diameters and/or orientationsof the eyes of the user 60. In some embodiments, one camera 500 isutilized for each eye, to separately determine the pupil size and/ororientation of each eye, thereby allowing the presentation of imageinformation to each eye to be dynamically tailored to that eye. In someother embodiments, the pupil diameter and/or orientation of only asingle eye 304 (e.g., using only a single camera 500 per pair of eyes)is determined and assumed to be similar for both eyes of the viewer 60.

For example, depth of field may change inversely with a viewer's pupilsize. As a result, as the sizes of the pupils of the viewer's eyesdecrease, the depth of field increases such that one plane notdiscernible because the location of that plane is beyond the depth offocus of the eye may become discernible and appear more in focus withreduction of pupil size and commensurate increase in depth of field.Likewise, the number of spaced apart depth planes used to presentdifferent images to the viewer may be decreased with decreased pupilsize. For example, a viewer may not be able to clearly perceive thedetails of both a first depth plane and a second depth plane at onepupil size without adjusting the accommodation of the eye away from onedepth plane and to the other depth plane. These two depth planes may,however, be sufficiently in focus at the same time to the user atanother pupil size without changing accommodation.

In some embodiments, the display system may vary the number ofwaveguides receiving image information based upon determinations ofpupil size and/or orientation, or upon receiving electrical signalsindicative of particular pupil sizes and/or orientations. For example,if the user's eyes are unable to distinguish between two depth planesassociated with two waveguides, then the controller 210 may beconfigured or programmed to cease providing image information to one ofthese waveguides. Advantageously, this may reduce the processing burdenon the system, thereby increasing the responsiveness of the system. Inembodiments in which the DOEs for a waveguide are switchable between onand off states, the DOEs may be switched to the off state when thewaveguide does receive image information.

In some embodiments, it may be desirable to have an exit beam meet thecondition of having a diameter that is less than the diameter of the eyeof a viewer. However, meeting this condition may be challenging in viewof the variability in size of the viewer's pupils. In some embodiments,this condition is met over a wide range of pupil sizes by varying thesize of the exit beam in response to determinations of the size of theviewer's pupil. For example, as the pupil size decreases, the size ofthe exit beam may also decrease. In some embodiments, the exit beam sizemay be varied using a variable aperture.

FIG. 5 shows an example of exit beams outputted by a waveguide. Onewaveguide is illustrated, but other waveguides in the waveguide assembly178 may function similarly, where the waveguide assembly 178 includesmultiple waveguides. Light 400 is injected into the waveguide 182 at theinput edge 382 of the waveguide 182 and propagates within the waveguide182 by TIR. At points where the light 400 impinges on the DOE 282, aportion of the light exits the waveguide as exit beams 402. The exitbeams 402 are illustrated as substantially parallel but they may also beredirected to propagate to the eye 304 at an angle (e.g., formingdivergent exit beams), depending on the depth plane associated with thewaveguide 182. Substantially parallel exit beams may be indicative of awaveguide with light extracting optical elements that outcouple light toform images that appear to be set on a depth plane at a large distance(e.g., optical infinity) from the eye 304. Other waveguides or othersets of light extracting optical elements may output an exit beampattern that is more divergent, which would require the eye 304 toaccommodate to a closer distance to bring it into focus on the retinaand would be interpreted by the brain as light from a distance closer tothe eye 304 than optical infinity.

FIG. 6 shows another example of the optical display system 100 includinga waveguide apparatus, an optical coupler subsystem to optically couplelight to or from the waveguide apparatus, and a control subsystem. Theoptical system 100 can be used to generate a multi-focal volumetric,image, or light field. The optical system can include one or moreprimary planar waveguides 1 (only one is shown in FIG. 6) and one ormore DOEs 2 associated with each of at least some of the primarywaveguides 1. The planar waveguides 1 can be similar to the waveguides182, 184, 186, 188, 190 discussed with reference to FIG. 4. The opticalsystem may employ a distribution waveguide apparatus, to relay lightalong a first axis (vertical or Y-axis in view of FIG. 6), and expandthe light's effective exit pupil along the first axis (e.g., Y-axis).The distribution waveguide apparatus, may, for example include adistribution planar waveguide 3 and at least one DOE 4 (illustrated bydouble dash-dot line) associated with the distribution planar waveguide3. The distribution planar waveguide 3 may be similar or identical in atleast some respects to the primary planar waveguide 1, having adifferent orientation therefrom. Likewise, the at least one DOE 4 may besimilar or identical in at least some respects to the DOE 2. Forexample, the distribution planar waveguide 3 and/or DOE 4 may becomprised of the same materials as the primary planar waveguide 1 and/orDOE 2, respectively. Embodiments of the optical display system 100 shownin FIG. 4 or 6 can be integrated into the wearable display system 100shown in FIG. 2.

The relayed and exit-pupil expanded light is optically coupled from thedistribution waveguide apparatus into the one or more primary planarwaveguides 10. The primary planar waveguide 1 relays light along asecond axis, in some cases orthogonal to first axis, (e.g., horizontalor X-axis in view of FIG. 6). Notably, the second axis can be anon-orthogonal axis to the first axis. The primary planar waveguide 1expands the light's effective exit pupil along that second axis (e.g.,X-axis). For example, the distribution planar waveguide 3 can relay andexpand light along the vertical or Y-axis, and pass that light to theprimary planar waveguide 1 which relays and expands light along thehorizontal or X-axis.

The optical system may include one or more sources of colored light(e.g., red, green, and blue laser light) 110 which may be opticallycoupled into a proximal end of a single mode optical fiber 9. A distalend of the optical fiber 9 may be threaded or received through a hollowtube 8 of piezoelectric material. The distal end protrudes from the tube8 as fixed-free flexible cantilever 7. The piezoelectric tube 8 can beassociated with 4 quadrant electrodes (not illustrated). The electrodesmay, for example, be plated on the outside, outer surface or outerperiphery or diameter of the tube 8. A core electrode (not illustrated)is also located in a core, center, inner periphery or inner diameter ofthe tube 8.

Drive electronics 12, for example electrically coupled via wires 10,drive opposing pairs of electrodes to bend the piezoelectric tube 8 intwo axes independently. The protruding distal tip of the optical fiber 7has mechanical modes of resonance. The frequencies of resonance candepend upon a diameter, length, and material properties of the opticalfiber 7. By vibrating the piezoelectric tube 8 near a first mode ofmechanical resonance of the fiber cantilever 7, the fiber cantilever 7is caused to vibrate, and can sweep through large deflections.

By stimulating resonant vibration in two axes, the tip of the fibercantilever 7 is scanned biaxially in an area filling two dimensional(2D) scan. By modulating an intensity of light source(s) 11 in synchronywith the scan of the fiber cantilever 7, light emerging from the fibercantilever 7 forms an image. Descriptions of such a set up are providedin U.S. Patent Publication No. 2014/0003762, which is incorporated byreference herein in its entirety.

A component of an optical coupler subsystem collimates the lightemerging from the scanning fiber cantilever 7. The collimated light isreflected by mirrored surface 5 into the narrow distribution planarwaveguide 3 which contains the at least one diffractive optical element(DOE) 4. The collimated light propagates vertically (relative to theview of FIG. 6) along the distribution planar waveguide 3 by totalinternal reflection, and in doing so repeatedly intersects with the DOE4. The DOE 4 in some cases has a low diffraction efficiency. This causesa fraction (e.g., 10%) of the light to be diffracted toward an edge ofthe larger primary planar waveguide 1 at each point of intersection withthe DOE 4, and a fraction of the light to continue on its originaltrajectory down the length of the distribution planar waveguide 3 viaTIR.

At each point of intersection with the DOE 4, additional light isdiffracted toward the entrance of the primary waveguide 1. By dividingthe incoming light into multiple outcoupled sets, the exit pupil of thelight is expanded vertically by the DOE 4 in the distribution planarwaveguide 3. This vertically expanded light coupled out of distributionplanar waveguide 3 enters the edge of the primary planar waveguide 1.

Light entering primary waveguide 1 propagates horizontally (relative tothe view of FIG. 6) along the primary waveguide 1 via TIR. As the lightintersects with DOE 2 at multiple points as it propagates horizontallyalong at least a portion of the length of the primary waveguide 10 viaTIR. The DOE 2 may advantageously be designed or configured to have aphase profile that is a summation of a linear diffraction pattern and aradially symmetric diffractive pattern, to produce both deflection andfocusing of the light. The DOE 2 may advantageously have a lowdiffraction efficiency (e.g., 10%), so that only a portion of the lightof the beam is deflected toward the eye of the view with eachintersection of the DOE 2 while the rest of the light continues topropagate through the waveguide 1 via TIR.

At each point of intersection between the propagating light and the DOE2, a fraction of the light is diffracted toward the adjacent face of theprimary waveguide 1 allowing the light to escape the TIR, and emergefrom the face of the primary waveguide 1. In some embodiments, theradially symmetric diffraction pattern of the DOE 2 additionally impartsa focus level to the diffracted light, both shaping the light wavefront(e.g., imparting a curvature) of the individual beam as well as steeringthe beam at an angle that matches the designed focus level.

Accordingly, these different pathways can cause the light to be coupledout of the primary planar waveguide 1 by a multiplicity of DOEs 2 atdifferent angles, focus levels, and/or yielding different fill patternsat the exit pupil. Different fill patterns at the exit pupil can bebeneficially used to create a light field display with multiple depthplanes. Each layer in the waveguide assembly or a stack of layers (e.g.,3 layers) may be employed to generate a respective color (e.g., red,blue, green). Thus, for example, a first stack of three adjacent layersmay be employed to respectively produce red, blue and green light at afirst focal depth. A second stack of three adjacent layers may beemployed to respectively produce red, blue and green light at a secondfocal depth. Multiple stacks may be employed to generate a full 3D or 4Dcolor image light field with various focal depths.

Other Components of AR Systems

In many implementations, the AR system may include other components inaddition to the display system 100. The AR devices may, for example,include one or more haptic devices or components. The haptic device(s)or component(s) may be operable to provide a tactile sensation to auser. For example, the haptic device(s) or component(s) may provide atactile sensation of pressure and/or texture when touching virtualcontent (e.g., virtual objects, virtual tools, other virtualconstructs). The tactile sensation may replicate a feel of a physicalobject which a virtual object represents, or may replicate a feel of animagined object or character (e.g., a dragon) which the virtual contentrepresents. In some implementations, haptic devices or components may beworn by the user (e.g., a user wearable glove). In some implementations,haptic devices or components may be held by the user.

The AR system may, for example, include one or more physical objectswhich are manipulable by the user to allow input or interaction with theAR system. These physical objects are referred to herein as totems. Sometotems may take the form of inanimate objects, for example a piece ofmetal or plastic, a wall, a surface of table. Alternatively, some totemsmay take the form of animate objects, for example a hand of the user. Asdescribed herein, the totems may not actually have any physical inputstructures (e.g., keys, triggers, joystick, trackball, rocker switch).Instead, the totem may simply provide a physical surface, and the ARsystem may render a user interface so as to appear to a user to be onone or more surfaces of the totem. For example, the AR system may renderan image of a computer keyboard and trackpad to appear to reside on oneor more surfaces of a totem. For instance, the AR system may render avirtual computer keyboard and virtual trackpad to appear on a surface ofa thin rectangular plate of aluminum which serves as a totem. Therectangular plate does not itself have any physical keys or trackpad orsensors. However, the AR system may detect user manipulation orinteraction or touches with the rectangular plate as selections orinputs made via the virtual keyboard and/or virtual trackpad.

Examples of haptic devices and totems usable with the AR devices, HMD,and display systems of the present disclosure are described in U.S.Patent Publication No. 2015/0016777, which is incorporated by referenceherein in its entirety.

Example Waveguide Display

FIG. 7A is a top view that schematically illustrates an example of adisplay 700 including a waveguide 905 that includes an incouplingoptical element 1007, a light distributing element 1011, and anoutcoupling optical element 1009. FIG. 7B schematically illustrates across-sectional view of the display 700 depicted in FIG. 7A along theaxis A-A′.

The waveguide 905 may be part of the stack of waveguides 178 in thedisplay system 100 shown in FIG. 4. For example, the waveguide 905 maycorrespond to one of the waveguides 182, 184, 186, 188, 190, and theoutcoupling optical element 1009 may correspond to the light extractingoptical elements 282, 284, 286, 288, 290 of the display system 100.

The display 700 is configured such that incoming incident light ofdifferent wavelengths represented by light rays 903 i 1, 903 i 2 and 903i 3 (solid, dashed, and dash-double-dotted lines, respectively) arecoupled into the waveguide 905 by the incoupling optical element 1007.The incoming incident light to the waveguide 905 can be projected froman image injection device (such as one of the image injection devices200, 202, 204, 206, 208 illustrated in FIG. 4). The incoupling opticalelement 1007 can be configured to couple wavelengths of the incidentlight into the waveguide 905 at appropriate angles that supportpropagation through the waveguide 905 by virtue of total internalreflection (TIR).

A light distributing element 1011 can be disposed in the optical pathalong which the different wavelengths of light 903 i 1, 903 i 2 and 903i 3 propagate through the waveguide 905. The light distributing element1011 can be configured to redirect a portion of the light from theincoupling optical element 1007 toward the outcoupling optical element1009, thereby enlarging the beam size of the interacting light along thedirection of propagation. Accordingly, the light distributing element1011 may be advantageous in enlarging the exit pupil of the display 700.In some embodiments, the light distributing element 1011 may thusfunction as an orthogonal pupil expander (OPE).

The outcoupling optical element 1009 can be configured to redirectincoupled light that is incident on the element 1009 out of the x-yplane of the waveguide 905 at appropriate angles (e.g., in thez-direction) and efficiencies to facilitate proper overlay of light atdifferent wavelengths and at different depth planes such that a viewercan perceive a color image of good visual quality. The outcouplingoptical element 1009 can have an optical power that provides adivergence to the light that exits through the waveguide 905 such thatthe image formed by the light that exits through the waveguide 905appears (to the viewer) to originate from a certain depth. Theoutcoupling optical element 1009 can enlarge the exit pupil of thedisplay 700 and may be referred to as an exit pupil expander (EPE) thatdirects light to the viewer's eye.

The incoupling optical element 1007, the outcoupling optical element1009, and the light distributing element 1011 can each include one ormore gratings, such as, for example, an analog surface relief grating(ASR), binary surface relief structures (BSR), volume holographicoptical elements (VHOE), digital surface relief structures, and/orvolume phase holographic material (e.g., holograms recorded in volumephase holographic material), or switchable diffractive optical elements(e.g., a polymer dispersed liquid crystal (PDLC) grating). Other typesof gratings, holograms, and/or diffractive optical elements, configuredto provide the functionality disclosed herein, may also be used. Invarious embodiments, the incoupling optical element 1007 can include oneor more optical prisms, or optical components including one or morediffractive elements and/or refractive elements. The various sets ofdiffractive or grating structures can be disposed on the waveguide byusing fabrication methods such as injection compression molding, UVreplication, or nano-imprinting of the diffractive structures.

The incoupling optical element 1007, the outcoupling optical element1009, or the light distributing element 1011 need not be a singleelement (e.g., as schematically depicted in FIGS. 7A, 7B, and 8) andeach such element can include a plurality of such elements. Theseelements can be disposed on one (or both) of the surfaces 905 a, 905 bof the waveguide 905. In the example shown in FIGS. 7A, 7B, and 8, theincoupling optical element 1007, the outcoupling optical element 1009,and the light distributing element 1011 are disposed on the surface 905a of the waveguide 905.

The light distributing element 1011 can be disposed adjacent the firstor the second surface 905 a or 905 b of the waveguide 905. In variousembodiments, the light distributing element 1011 can be disposed suchthat it is spaced apart from the outcoupling optical element 1009,although the light distributing element 1011 need not be so configuredin some embodiments. The light distributing element 1011 can beintegrated with one or both of the first or the second surface 905 a or905 b of the waveguide 905. In some embodiments, as disclosed herein,the light distributing element 1011 may be disposed in the bulk ofwaveguide 905.

In some embodiments, one or more wavelength selective filters may beintegrated with or disposed adjacent to the incoupling optical element1007, the outcoupling optical element 1009, or the light distributingelement 1011. The display 700 illustrated in FIG. 7A includes thewavelength selective filter 1013, which is integrated into or on asurface of the waveguide 905. The wavelength selective filters can beconfigured to attenuate some portion of light at the one or morewavelengths that may be propagating along various directions in thewaveguide 905. As will be further described herein, the wavelengthselective filters can be absorptive filters such as color band absorbersor distributed switches (e.g., electro-optic materials).

Examples of Waveguides Using Wavelength Selective Filters

Light can be separated into constituent colors (e.g., red (R), green(G), and blue (B)), and it may be desirable to send differentconstituent colors to different layers of the waveguide assembly. Forexample, each of the depth planes of the waveguide assembly maycorrespond to one or more layers to display particular colors of light(e.g., R, G, and B layers). As an example, a waveguide assembly havingthree depth planes, with each depth plane comprising three colors (e.g.,R, G, and B), would include nine waveguide layers. Other numbers ofdepth planes and/or color layers per depth plane are available. Thewaveguide assembly can be configured to send light of the appropriatecolor to a particular layer in a particular depth plane (e.g., red lightfor a red color layer in a particular depth plane). It may be desirableif the light propagating in a particular color layer (e.g., a red layer)is substantially all in the desired color (e.g., red) with littleadmixture of other colors (e.g., blue or green) in that color layer. Aswill be further described below, various implementations of thewaveguide assembly can be configured to filter out undesired wavelengthsof light in particular waveguide layers so that substantially only asingle color (the desired color) propagates in that layer. Some suchimplementations may advantageously provide better color separation amongthe different color layers and lead to more accurate colorrepresentation by the display. Accordingly, color filters may be used tofilter out the undesired constituent colors at different depth planes.

As described with reference to FIG. 7A, certain wavelengths of the lightcan be deflected (e.g., refracted, reflected, or diffracted) at a firstlayer of the incoupling optical element 1007 into a first waveguide. Insome designs, the incoupling optical element 1007 includes two or moreincoupling optical elements. For example, light may be deflected by afirst incoupling optical element into a first waveguide of a waveguidestack while other wavelengths may be transmitted to other layers of theincoupling optical element to be directed to other waveguides in thestack. For example, the first layer of the incoupling optical elementmay be configured to deflect red light into the first waveguide(configured for red light) while transmitting other wavelengths (e.g.,green and blue) to other layers of the waveguide stack.

However, the incoupling optical elements may not always be perfectlyconfigured to deflect all of the light at the given wavelength ortransmit all of the light at the other wavelengths. For example, whilethe first layer of the incoupling optical element may be configured todeflect primarily red light, physical limitations may inadvertentlycause the first layer of the incoupling optical element to deflect anamount of other wavelengths (e.g., green and blue) into the firstwaveguide of the stack. Similarly, some of the red light may betransmitted through the first layer of the incoupling optical element toother layers of the incoupling optical elements and be deflected intothe associated waveguides (e.g., into green and blue waveguides).

To compensate for these imperfections, one or more portions of thewaveguide stack can include a region that is configured to filter out orattenuate an unwanted wavelength or to isolate a desired wavelength. Forexample, the first waveguide may be configured to propagate red light,so the waveguide may include a region (e.g., a tinted or dyed region)that is configured to attenuate the green and blue light in order toisolate the red light. In some implementations, the light distributingelement 1011 includes (or is included in) the tinted or dyed region

The region in and around the light distributing element 1011 may providea greater volume than the incoupling optical element 1007 through whichlight may propagate. Providing the filtering functionality in the regionof the light distributing element 1011 can allow the light manipulationaction (e.g., filtering) to operate over a longer path length (whichmakes the filtering more effective) and/or reduce interferences alongthe primary optical path (e.g., the incoupling optical element 1007 andthe outcoupling optical element 1009).

FIG. 8 is a top view that schematically illustrates an example of adisplay 700 including a waveguide 905 that is generally similar todisplay shown in FIGS. 7A and 7B. The waveguide 906 includes theincoupling optical element 1007, the light distributing element 1011,and the outcoupling optical element 1009. The waveguide 905 alsoincludes a wavelength selective region 924 that can selectivelypropagate certain wavelengths of light while selectively attenuatingother wavelengths of light. For example, the wavelength selective regioncan include a color filter. In the example shown in FIG. 8, thewavelength selective region 924 can be disposed in and/or distributedthrough a region of the waveguide 905 in or around the lightdistributing element 1011. For example, light received from theincoupling optical element 1007 can be selectively filtered by thewavelength selective region 924 before being propagated to theoutcoupling optical element 1009.

The wavelength selective region 924 represents a portion of thewaveguide 905 that includes a distributed filter and/or switch materialin at least some part. In some embodiments, the wavelength selectiveregion 924 includes a plurality of wavelength selective regions. Asshown in the example in FIG. 8, the wavelength selective region 924represents the only portion of the optical path that includes awavelength selective filter, such that, e.g., the incoupling opticalelement 1007 and the outcoupling optical element 1009 do not includewavelength selective filters. Because the light exiting the outcouplingoptical element 1009 can include light from the world 144, theoutcoupling optical element 1009 may not include a wavelength selectiveregion so that the light from the world is not colored or tinted.Similarly, in order to maintain the composition of the incoming lightinto it, the incoupling optical element 1007 may optionally also not beselective for wavelength.

It may be advantageous to tint or dye layers of the light distributingelement 1011 and not the incoupling optical element 1007 or theoutcoupling optical element 1009. If the light is tinted before itenters the incoupling optical element 1007, this may attenuate theintensity of the incoupled light. If the incoupling optical element 1007is tinted, the light may be coupled to the wrong waveguide. If theoutcoupling optical element 1009 is tinted, light from the outside worldthat passes through the display 700 may be tinted or filtered, which maylead to distortions in the viewer's perception of the outside world.Each of these examples may be undesirable in certain designs.

FIG. 9 illustrates a perspective view of an example stack 1200 ofwaveguides. The view along the axis A-A′ in FIG. 9 is generally similarto the view shown in FIG. 7B. In this example, the stack 1200 ofwaveguides includes waveguides 1210, 1220, and 1230. The layers of alight distributing element 1210, 1220, 1230 can correspond to the lightdistributing element 1011 in FIG. 8. As illustrated, each waveguide caninclude an associated layer of the incoupling optical element, with,e.g., the layer of the incoupling optical element 1212 disposed on asurface (e.g., a bottom surface) of the waveguide 1210, the layer of theincoupling optical element 1224 disposed on a surface (e.g., a bottomsurface) of the waveguide 1220, and the layer of the incoupling opticalelement 1232 disposed on a surface (e.g., a bottom surface) of thewaveguide 1230. One or more of the layers of the incoupling opticalelement 1212, 1222, 1232 may be disposed on the top surface of therespective waveguide 1210, 1220, 1230 (particularly where the one ormore layers of the incoupling optical element are optically transmissiveand/or deflective). Similarly, the other incoupling optical elements1222, 1232 may be disposed on the bottom surface of their respectivewaveguide 1220, 1230 (or on the top surface of the next lowerwaveguide). In some designs, the layers of the incoupling opticalelement 1212, 1222, 1232 are disposed in the volume of the respectivewaveguide 1210, 1220, 1230.

The incoupling optical elements 1212, 1222, 1232 may include awavelength selective filter, such as a filter that selectively reflects,refracts, transmits, and/or diffracts one or more wavelengths of light,while transmitting, diffracting, refracting, and/or reflecting otherwavelengths of light. Examples of wavelength selective filters includecolor filters such as dyes, tints, or stains. The wavelength selectivefilter can include a dichroic filter, a Bragg grating, or a polarizer.The wavelength selective filter may include a bandpass filter, ashortpass filter, or a longpass filter. Some wavelength selectivefilters can be electronically switchable. While illustrated on one sideor corner of their respective waveguide 1210, 1220, 1230, the layers ofthe incoupling optical element 1212, 1222, 1232 may be disposed in otherareas of their respective waveguide 1210, 1220, 1230 in otherembodiments. The waveguides 1210, 1220, 1230 may be spaced apart andseparated by gas (e.g., air), liquid, and/or solid layers of material.

With continued reference to FIG. 9, light rays 1240, 1242, 1244 areincident on the stack 1200 of waveguides. The stack 1200 of waveguidesmay be part of the stack of waveguides in the display system 100 (FIG.4). For example, the waveguides 1210, 1220, 1230 may correspond to threeof the waveguides 182, 184, 186, 188, 190, and the light rays 1240,1242, 1244 may be injected into the waveguides 1210, 1220, 1230 by oneor more image injection devices 200, 202, 204, 206, 208.

In certain embodiments, the light rays 1240, 1242, 1244 have differentproperties, e.g., different wavelengths or ranges of wavelengths, whichmay correspond to different colors. The layers of the incoupling opticalelement 1212, 122, 1232 can be configured to selectively deflect thelight rays 1240, 1242, 1244 based upon a particular feature of theproperty of light, (e.g., wavelength, polarization) while transmittinglight that does not have that property or feature. In some embodiments,the layers of the incoupling optical element 1212, 122, 1232 eachselectively deflect one or more particular wavelengths of light, whiletransmitting other wavelengths. The non-deflected light may propagateinto a different waveguide and/or waveguide layer.

For example, the layer of the incoupling optical element 1212 may beconfigured to selectively deflect a light ray 1240, which has a firstwavelength or range of wavelengths, while transmitting the light rays1242 and 1244, which have different second and third wavelengths orranges of wavelengths, respectively. As shown in FIG. 9, the deflectedlight rays 1240, 1242, 1244 are deflected so that they propagate throughthe corresponding waveguide 1210, 1220, 1230; that is, the layers of theincoupling optical element 1212, 1222, 1232 of each respective waveguidecouple (e.g., deflect) light into the corresponding waveguide 1210,1220, 1230. The light rays 1240, 1242, 1244 are deflected at angles thatcause the light to propagate through the respective waveguide 1210,1220, 1230 (e.g., by TIR).

The light rays 1240, 1242, 1244 are incident on the corresponding layerof the light distributing element 1214, 1224, 1234. The layers of thelight distributing element 1214, 1224, 1234 deflect the light rays 1240,1242, 1244 so that they propagate towards the corresponding layer of theoutcoupling optical element 1250, 1252, 1254.

In some embodiments, an angle-modifying optical element 1260 may beprovided to alter the angle at which the light rays 1240, 1242, 1244strike the layers of the incoupling optical element. The angle-modifyingoptical element can cause the light rays 1240, 1242, 1244 to impinge onthe corresponding layer of the incoupling optical element 1212, 1222,1232 at angles appropriate for TIR. For example, in some embodiments,the light rays 1240, 1242, 1244 may be incident on the angle-modifyingoptical element 1260 at an angle normal to the waveguide 1210. Theangle-modifying optical element 1260 then changes the direction ofpropagation of the light rays 1240, 1242, 1244 so that they strike thelayers of the incoupling optical elements 1212, 1222, 1232 at an angleof less than 90 degrees relative to the surface of waveguide 1210. Theangle-modifying optical element 1260 may include a grating, a prism,and/or a mirror.

FIG. 10A is a side view that schematically illustrates an exampledisplay where two waveguides 1210, 1220 of the light distributingelement 1011 include color filters 1060 a, 1060 b. The number ofwaveguides in a given embodiment of the light distributing element 1011could be greater or fewer than two. As a light beam 1360 enters thedisplay, part of the light is deflected into the first waveguide 1210while some of the light continues propagating until it is deflected intothe second waveguide 1220. The incoming light beam 1360 (e.g., whitelight) may include multiple wavelengths 1354, 1358 of light (representedby different dashing patterns in FIG. 10A), which may comprisewavelengths λ1 and λ2. The number of constituent light beams may begreater or fewer than two. For example, λ1 and λ2 may representdifferent colors of light that are being injected into the display(e.g., blue and green). Any combination of colors can be described by λ1and λ2. The incoming light beam 1360 can comprise visible light, or invarious implementations, non-visible light such as infrared orultraviolet light.

As shown in the example in FIG. 10A, the waveguides 1210, 1220 includecolor filters 1060 a, 1060 b. Each waveguide 1210, 1220 may beassociated with a particular design wavelength. This can mean that awaveguide that is associated with a design wavelength includes anincoupling optical element that is configured to deflect light at thedesign wavelength to an associated layer of the light distributingelement and/or that the associated wavelength selective region isconfigured to attenuate light not at the design wavelength. As shown inFIG. 10A, for example, the first waveguide 1210 may have λ1 as a designwavelength, and the second waveguide 1220 may have λ2 as a designwavelength. In this example, the first layer of the incoupling opticalelement 1212 would be configured to deflect λ1 to the first layer of thelight distributing element 1214, and the second layer of the incouplingoptical element 1222 would be configured to deflect λ2 to the secondlayer of the light distributing element 1224.

The color filters 1060 a, 1060 b can be designed or tuned to purify orisolate a desired wavelength or set of wavelengths for the correspondingwaveguide 1210, 1220. Alternatively, the color filters 1060 a, 1060 bcan attenuate undesired wavelengths. For example, the first color filter1060 a may include a tint that attenuates red light. Similarly, thesecond color filter 1060 b may include a tint that attenuates greenlight. The color filters 1060 a, 1060 b can optionally be electronicallyswitchable so that they attenuate light when they are switched on and donot attenuate light when switched off. Examples of color filters includematerials that are dyed, tinted, or stained. Color filters mayoptionally include a dichroic filter or a Bragg grating.

References to a given color of light throughout this disclosure will beunderstood to encompass light of one or more wavelengths within a rangeof wavelengths of light that are perceived by a viewer as being of thatgiven color. For example, red light may include light of one or morewavelengths in the range of about 620-780 nm, green light may includelight of one or more wavelengths in the range of about 492-577 nm, andblue light may include light of one or more wavelengths in the range ofabout 435-493 nm. The waveguides described herein can be configured tooperate on wavelength bands outside the visual, e.g., infrared orultraviolet. Similarly, the term “a wavelength” should be understood tomean “a single wavelength” or “a range of wavelengths” in variousimplementations. For example, the wavelength represented by λ1 mayrepresent blue light, which may include light of one or more wavelengthsin the range of about 450-470 nm.

As depicted in FIG. 10A, each waveguide 1210, 1220 may be associatedwith a particular color filter 1060 a, 1060 b. When the incoming lightbeam 1360 enters the incoupling optical element 1007 and reaches a firstlayer of the incoupling optical element 1212, the first constituentlight beam 1354 is deflected (e.g., refracted, reflected, or diffracted)at least in part due to its wavelength λ1. In some instances, anundeflected first constituent light beam 1354 b may be transmittedthrough the first layer of the incoupling optical element 1212 at leastin part due to its λ1 not being fully optically interactive with thefirst layer of the incoupling optical element 1212. When the incominglight beam 1360 reaches the first layer of the incoupling opticalelement 1212, a second constituent light beam 1358 is transmitted atleast in part due to its wavelength λ2. In some instances, an amount ofan untransmitted second constituent light beam 1358 b may deflect offthe first layer of the incoupling optical element 1212 at least in partdue to its λ2 being optically interactive with the first layer of theincoupling optical element 1212.

With continued reference to FIG. 10A, in certain embodiments, a firstresultant light beam 1360 a includes a first target light beam 1354 a,which is at the design wavelength for the first waveguide 1210, and theuntransmitted second constituent light beam 1358 b, which is not at thedesign wavelength for the first waveguide. In certain embodiments, inorder to attenuate the intensity of the untransmitted second constituentlight beam 1358 b, the first waveguide 1210 includes a first colorfilter 1060 a as described herein. Due at least in part to the firstcolor filter 1060 a, as schematically depicted in FIG. 10A, theintensity of the untransmitted second constituent light beam 1358 b maybe attenuated as it propagates through the first waveguide 1210. Incertain embodiments, the intensity of the untransmitted secondconstituent light beam 1358 b is attenuated relative to the first targetlight beam 1354 a. The first layer of the light distributing element1214 can be configured to deflect the first target light beam 1354 a toan associated layer of the outcoupling optical element (not shown).

Similarly, in some embodiments, a second resultant light beam 1360 b mayinclude a second target light beam 1358 a, which is at the designwavelength for the second waveguide 1220, and the undeflected firstconstituent light beam 1354 b, which is not at the design wavelength forthe second waveguide 1220. In certain embodiments, in order to attenuatethe intensity of the undeflected first constituent light beam 1354 b,the first waveguide 1210 includes a second color filter 1060 b asdescribed herein. Due at least in part to the second color filter 1060b, as schematically depicted in FIG. 10A, the intensity of theundeflected first constituent light beam 1354 b can be attenuated as itpropagates through the second waveguide 1220. In certain embodiments,the intensity of the undeflected first constituent light beam 1354 b isattenuated relative to the second target light beam 1358 a. The secondlayer of the light distributing element 1224 can be configured todeflect the second target light beam 1358 a to an associated layer ofthe outcoupling optical element (not shown).

The light 1360 may enter the waveguide stack and be coupled into aproximal surface of the first waveguide 1210. The first layer of theincoupling optical element 1212 may be disposed on a distal surface ofthe first waveguide 1210 and/or on a proximal surface of the secondwaveguide 1220. In some designs, the first layer of the incouplingoptical element 1212 is disposed within the volume of the firstwaveguide 1210. The first layer of the incoupling optical element may bedisposed parallel to one or both of the proximal and distal surfaces ofthe first waveguide 1210. As shown, the proximal surface and the distalsurface of the first waveguide are parallel to one another. In someconfigurations, the proximal surface may not be parallel to the distalsurface. The first layer of the incoupling optical element 1212 may bedisposed at an angle relative to the distal surface and/or proximalsurface of the first waveguide 1210.

FIG. 10B schematically illustrates a side view of an example displaywhere two waveguides 1210, 1220 include distributed switch materials1070 a, 1070 b. The number of waveguides in a given embodiment could begreater or fewer than two. In certain embodiments, the waveguides 1210,1220 include distributed filter and/or switch material, such as switchmaterials 1070 a, 1070 b. Examples of switch materials include dichroicfilters, electronically switchable glass, and electronically switchablemirrors. The switch materials 1070 a, 1070 b can be electronicallyswitched to modify, e.g., the brightness, polarization, angle ofreflection, or angle of refraction of light. Some switch materials mayalso include electrochromic, photochromic, thermochromic, suspendedparticle, or micro-blind materials, or polymer dispersed liquidcrystals. For example, electrochromic elements may be used to modify thebrightness and/or intensity of light. As a further example, a polymerdispersed liquid crystal grating or other tunable grating may be used tomodify an angle at which light is propagated through the waveguide. Theswitch materials can be designed or tuned to attenuate light of unwantedcolors or wavelengths. For example, the first switch material 1070 a mayinclude a filter that attenuates blue light by disrupting thepropagation of blue light. As a second example, the first switchmaterial 1070 a can include a filter that attenuates colors of lightthat are not blue by disrupting the propagation of the light at thosewavelengths. In some embodiments, the switch materials 1070 a, 1070 bare electronically switchable to attenuate light when they are switchedon and not attenuate light when switched off. The propagation of lightmay be disrupted, for example, by causing the light to become absorbed,by altering the index of refraction of the material in a way thatprevents the light from propagating by total internal reflection, and/orby substantially altering the path angle of the light.

A first switch material 1070 a may be disposed as a layer on a distalsurface of the first waveguide 1210, as shown in FIG. 10B, and/or on aproximal surface of the second waveguide 1220 (e.g., in a stackedwaveguide configuration). In some designs, the first switch material1070 a is disposed on a proximal surface of the first waveguide 1210. Asshown, the first switch material 1070 a may be disposed parallel to theproximal surface of the waveguide. In some designs, the first switchmaterial 1070 a is oriented at an angle relative to the distal and/orproximal surface of the waveguide 1210. The first switch material 1070 amay be disposed within the volume of the first waveguide 1210. Forexample, the switch material may disposed along a plane intersecting oneor more surfaces of the first waveguide 1210 and/or or may be disposedvolumetrically (e.g., throughout the whole volume) in the firstwaveguide material (e.g., mixed and/or patterned into the firstwaveguide material). The first switch material 1070 a may include amaterial that alters the index of refraction and/or absorption of lightfor certain ranges of wavelengths.

As illustrated by FIG. 10B, the first switch material may be disposedalong a plane perpendicular to entering light rays 1360 and/or parallelto the first layer of the incoupling optical element 1212. In somedesigns, the first switch material is disposed along two or moresurfaces of the first waveguide 1210, such as, for example, adjacentsurfaces and/or opposite surfaces (e.g., proximal and distal surfaces).

Distributed switch materials may be used to steer a beam (e.g., beforebeing outcoupled by the outcoupling optical element). Beam steering mayallow expanding the field of view of a user. In some examples, a polymerdispersed liquid crystal grating or other tunable grating may beimplemented as distributed switch materials and used to perform beamsteering by modifying an angle of TIR waveguided light, an angle atwhich light is outcoupled by the outcoupling optical element, or acombination thereof. Switch materials can be used to modulate lightreceived from upstream components (e.g., light source, LCoS). Differentwaveguides or layers of the light distributing element may beindependently electronically switched (e.g., by the controller 210). Forexample, it may be advantageous to modulate light in one waveguide whileallowing light in a second waveguide to propagate unmodulated. Thus, insome embodiments, modulation processes that are typically performed bythe upstream components can be performed at the waveguide stack throughstrategic control of the distributed switches. Accordingly, outcouplingcan be enabled or disabled on a waveguide-by-waveguide basis bycontrolling the associated distributed switches.

In some embodiments, one or more metasurfaces (e.g., made frommetamaterials) may be used for beam control (e.g., beam steering).Further information on metasurfaces and metamaterials that may be usedas distributed switch materials in various embodiments of thisdisclosure can be found in U.S. Patent Publication No. 2017/0010466and/or U.S. Patent Publication No. 2017/0010488, both of which arehereby incorporated by reference herein in their entireties.

FIG. 11 illustrates a schematic of an example waveguide 1210 withmultiple filter regions 1104. The filter regions 1104 may be colorfilters and/or switch materials. Additional wavelength selective filtersmay also be present in the waveguide 1210. The filter regions 1104 caninclude any volumetric optical filters as described herein.

Examples of Wavelength Multiplexing Displays

The wavelengths that comprise a light beam can be filtered into a seriesof waveguides through wavelength multiplexing. Wavelength multiplexingcan allow images to be sent to different waveguides simultaneously,e.g., by using or modulating laser diodes at different wavelengthssimultaneously. This can result in a simple switching method thataddresses different display waveguides. It can enable a rich light fieldwhere photons appear to arrive from different depth planessimultaneously.

As described herein, each waveguide in the display can correspond to aparticular depth plane of an image. For monochromatic depth planes, onlyone waveguide may be necessary for the depth plane. However, for depthplanes that can create multi-color images, each depth plane can beassociated with a stack of waveguides configured to display differentcolors. For example, each depth plane may include a stack of threewaveguides associated with red (R) light, green (G) light, and blue (B)light. To achieve this, it may be desirable to split light into separatecolors (e.g., red, green, blue) as well as into subcolors.

Subcolors, as used herein, refer to wavelengths or ranges of wavelengthsfalling substantially within the range of wavelengths encompassed by theassociated color. For example, the green color may span the range ofwavelengths from about 495 nm to 570 nm. Thus, the human eye tends toidentify as green those wavelengths that contain primarily wavelengthsin that range. Continuing with this example, a green subcolor couldinclude a range of wavelengths from 500 nm to 510 nm, from 525 nm to 560nm, from 555 nm to 560 nm, etc. Humans may see substantially the samecolor when they view subcolors whose peak intensities are near eachother. Subcolors, within a color, have wavelength subranges that arewithin the wavelength range of the color, and different subcolors havedifferent wavelength subranges that may, or may not, at least partiallyoverlap in wavelength.

FIG. 12 illustrates an example of a series of subcolors 2204 within acolor 2200. As shown in FIG. 12, the color 2200 spans wavelengths ofapproximately 495 nm to 570 nm. For example, this color represents asource of green light with a peak intensity at about 530 nm. The shapeand dimensions of the intensity profile for this color is merely anexample, and it may take on other shapes and dimensions.

Subcolors 2204 of the color 2200 illustrate examples of other intensityprofiles that may still be considered “green” to human observers. Thewidth 2212 of the curve of each subcolor 2204 is narrower than that ofthe color 2200. Each subcolor 2204 can have a width 2212 and a peakwavelength 2208, but for clarity the width 2212 and peak wavelength 2208are not labeled for each subcolor. The width 2212 of each subcolor canbe represented by, e.g., the full width at half maximum (FWHM). Thedistance between peak wavelengths 2208 of each subcolor 2204 can bebetween about 1-120 nm. In some embodiments, the distance between peakwavelengths can be in a range of about 10-80 nm. In some embodiments,the distance between peak wavelengths can be between about 15-50 nm. Thewidth 2212 of each subcolor 2204 can be between about 3-35 nm, betweenabout 5-55 nm, less than 20 nm, less than 30 nm, less than 40 nm, orsome other width. The number and widths of subcolors can be selectedbased on the multiplexing properties of the display device.

With continued reference to FIG. 12, the color 2200 approximates aGaussian curve, though other curves and beam profiles are possible. Asshown in FIG. 12, the color 2200 can be described by its peak wavelength2216 and width 2220 (e.g., a full-width at half maximum (FWHM)). Thewidth 2216 can vary according to different embodiments. For example, thewidth 2216 can range between about 40-220 nm. In some embodiments, thewidth can range between about 15-120 nm, between about 60-160, betweenabout 45-135 nm, less than 10 nm, or greater than 175 nm.

Some embodiments permit the use of color ranges outside the visiblespectrum (e.g., ultraviolet, infrared). In part for that reason, it canmake sense to describe the relationship of the widths of the colors tothe subcolors in various embodiments. For example, in some embodimentsthe ratio of the width 2216 of a color to the width 2208 of a subcolorcan be in a range from about 2 to 5. In some embodiments, this ratio canbe between about 4-12, between about 10-25, be less than 2, or begreater than 25.

References to a given color or color of light throughout this disclosureencompass light of one or more wavelengths within a range of wavelengthsof light that are perceived by a viewer as being of that given color.For example, red light may include light of one or more wavelengths inthe range of about 620-780 nm, green light may include light of one ormore wavelengths in the range of about 495-570 nm, and blue light mayinclude light of one or more wavelengths in the range of about 435-495nm. The waveguides described herein can be configured to operate onwavelength bands outside the visual, e.g., infrared or ultraviolet. Theterm “wavelength” can mean “a single wavelength” or “a range ofwavelengths” in various implementations.

FIG. 13 schematically illustrates a side view of an example stackedwaveguide assembly 178. FIG. 13 shows two waveguide stacks 960 a, 960 b.There can be more than two waveguide stacks in other implementations. Asshown in FIG. 13, each waveguide stack 960 a, 960 b includes threewaveguides, but the waveguide stacks 960 a, 960 b may comprise one, two,four, or more waveguides and is not limited by the illustration in FIG.13. Each waveguide stack 960 a, 960 b may produce a different depthplane 306, as shown in FIG. 3.

In some embodiments, the waveguide stacks 960 a, 960 b may each beassociated with a particular depth plane in a light field display. Forexample, the waveguide stack 960 a may be used to display imagesperceivable at a first distance from the wearer, and the waveguide stack960 b may be used to display images perceivable at a second distancefrom the wearer, where the second distance is different from the firstdistance. Each waveguide stack 960 a, 960 b can be designed to displayone or more colors. In the example shown in FIG. 13, each stack 960 a,960 b includes three waveguides for three different colors (e.g., red,green, and blue).

As shown in FIG. 13, each waveguide stack may be associated withparticular subcolors. For example, the first waveguide stack 960 a maybe associated with a first subcolor of three different colors, e.g.,blue, green, and red. As depicted in FIG. 13, a first pair of light rays952 a, 952 b can represent two subcolors of the same color. For example,the first pair of light rays 952 a, 952 b may represent light at twosubcolors of blue, such as 440 nm and 450 nm light.

Each waveguide in the stacked waveguide assembly 178 can be configuredto receive light at a particular design wavelength. Generally, thedesign wavelength corresponds to a particular subcolor. As illustratedin FIG. 13, each waveguide 962 a, 966 a, 968 a, 962 b, 966 b, 968 b cancomprise a corresponding incoupling optical element 1007 a, 1007 b, 1007c, 1007 d, 1007 e, 1007 f. The incoupling optical element 1007 comprisesthe incoupling optical elements 1007 a, 1007 b, 1007 c, 1007 d, 1007 e,1007 f. Each incoupling optical element 1007 a, 1007 b, 1007 c, 1007 d,1007 e, 1007 f can be configured to deflect a design wavelength into thecorresponding waveguide 962 a, 966 a, 968 a, 962 b, 966 b, 968 b.

With reference to the waveguide stacks shown in FIG. 13, it can bechallenging to propagate light of the right color to the right colorplane in the right depth plane. For example, the display may attempt toshow a blue object that is at a particular depth from the viewer of thedisplay. In FIG. 13, rays 952 a and 952 b may represent the propagationof blue light. If a fraction of the blue light (e.g., the ray 952 a)that should be displayed at a first depth plane (e.g., 960 a) ismisdirected to a different depth plane (e.g., 960 b), then the resultingimage displayed to a viewer of the waveguide 905 will not accuratelyreflect the depth of the blue object in the image. Similarly, if afraction of the blue light that should be displayed at a blue colorlayer (e.g., layer 962 a) in the waveguide stack 960 a is misdirected toa red or green layer (e.g., layers 966 a, 968 a), then the color of theblue object will not be accurately displayed to the viewer. One possiblereason for the misdirection of light of a particular color to a “wrong”layer is that diffraction gratings, which may be used to diffract thelight from an incident direction (e.g., downward as shown in FIG. 13) toa propagation direction in the waveguide layer (e.g., horizontal asshown in FIG. 13), are not 100% efficient. Moreover, optical gratingsoften diffract light having wavelengths across a broad spectrum and mayaffect light of wavelengths that were not intended. For example,gratings tuned to diffract light of one color (e.g., red) may diffractlight of other colors (e.g., blue or green). Therefore, for example, asmall fraction of the light in the ray 952 a, which should be directedby the incoupling optical element 1007 a into the layer 926 a, may passthrough the incoupling optical element 1007 a and be directed into one(or more) of the other layers of the waveguide. Similar considerationsapply for green or red light input into the incoupling optical element1007.

Accordingly, certain embodiments of the display use a wavelengthmultiplexing technique to direct light to the appropriate layer in thewaveguide. For example, the wavelengths used for blue light rays 952 aand 952 b may be slightly different from each other and representdifferent subcolors of the color blue. Similarly, the wavelengths usedfor green light rays 956 a and 956 b may be slightly different from eachother and represent different subcolors of the color green. Finally, thewavelengths used for red light rays 958 a and 958 b may be slightlydifferent from each other and represent different subcolors of the colorred. The incoupling optical elements 1007 a-1007 f can be configured tostrongly re-direct light of the appropriate wavelength into thecorresponding layer in the waveguide assembly. Light that passes throughthe incoupling element will have a much lower likelihood of beingmisdirected by a different incoupling element, because the differentelement is configured to re-direct a different range of wavelengths.

For example, the blue light ray 952 a can be centered at a range ofwavelengths around 435 nm (e.g., a first blue subcolor), while the bluelight ray 952 b can be centered at a different range of wavelengthsaround 445 nm (e.g., a second blue subcolor). The incoupling opticalelement 1007 a can be configured to re-direct blue light of the firstblue subcolor, while the incoupling optical element 1007 d can beconfigured to re-direct blue light of the second blue subcolor. In thisway, the blue light ray 952 a is preferentially re-directed into thelayer 962 a, while the blue light ray 952 b is preferentiallyre-directed into the layer 962 b. Similar considerations apply to theuse of different green subcolors for the green light rays 956 a, 956 band different red subcolors for the red light rays 958 a, 958 b.

The foregoing is merely an example, and as shown in FIG. 12, manydifferent subcolors of a particular color can be used to multiplex lightof that color into the appropriate layers of the waveguide 905. Thewidth of the wavelength range of a subcolor can be selected so that theincoupling optical element can efficiently redirect the subcolor intothe appropriate layer. Likewise, the properties of the incouplingoptical element (e.g., a diffractive grating period) can be selected toefficiently re-direct light of the appropriate subcolor.

With further reference to FIG. 13, the first waveguide stack 960 a cancouple a first subcolor of three colors, such as blue, green, and red.Similarly, the second waveguide stack 960 b can couple a second subcolorof the three colors. For example, the first waveguides 962 a, 962 b ofeach stack can be configured to receive the first and second subcolorsof a first color, such as blue. Similarly, the second waveguides 966 a,966 b of each stack can be configured to receive the first and secondsubcolors of a second color, such as green.

In certain embodiments, subcolors of the same color may propagatethrough adjacent waveguides. Such waveguides may form a waveguide stackdedicated to a particular color. For example, a first waveguide may havea first subcolor of blue as a design wavelength and a second waveguidemay have a second subcolor of blue as the design wavelength. A thirdwaveguide may have a first subcolor of a second color (e.g., green).Thus, subcolors of a first wavelength (e.g., blue) may be grouped into afirst stack of waveguides and subcolors of a second wavelength (e.g.,green) may be grouped in a second stack of waveguides.

The number of waveguide stacks can be greater than two, and the numberof waveguides within each waveguide stack can be two or greater. Threedesign wavelength waveguides per waveguide stack are illustrated in FIG.13 as an example of where one color of each of three primary colors,such as blue, green, and red, are incoupled within each waveguide stack.However, this is not intended to limit the number of waveguides,waveguide stacks, or types of colors that can be incoupled.

Once the light at the color of the corresponding wavelength is incoupledinto the corresponding design wavelength waveguide and out of theincoupling optical element 980, the light propagates through thecorresponding waveguide 962 a, 966 a, 968 a, 962 b, 966 b, 968 b. Alongthe optical path of the light at the design wavelength is acorresponding light distributing element 1011 a, 1011 b, 1011 c, 1011 d,1011 e, 1011 f. The corresponding light distributing element 1011 a,1011 b, 1011 c, 1011 d, 1011 e, 1011 f can deflect the light at thecorresponding design wavelength to a corresponding layer of theoutcoupling optical element (not shown). The corresponding layer of theoutcoupling optical element is configured to couple the light at thecorresponding design out of the stacked waveguide assembly.

FIG. 14 schematically illustrates a side view of an example stackedwaveguide assembly 178 with a preliminary light filter system 1080. Thepreliminary light filter 1080 can be used to provide a first-order colorselection process. The preliminary light filter system 1080 can comprisea number of optical elements 1084 a, 1084 b, 1088 a, 1088 b, such asgratings, mirrors, prisms, and other refractive and/or reflectiveelements. The filter system 1080 may include diffractive opticalelements as well. The precise number and configuration of the opticalelements is shown here by way of example only and may be changed asnecessary. The filter system 1080 can be used to direct light ofdifferent wavelengths to different color layers or depth planes of thewaveguide 905.

Examples of Display Systems with Wavelength Multiplexing and WavelengthSelective Filtering

Features of both wavelength multiplexing and wavelength selectivefilters may be included in a waveguide display system. A wavelengthmultiplexing waveguide assembly can include one or more wavelengthselective filters. FIG. 15A shows the waveguide assembly 178 of FIG. 13with distributed filters 1502 a, 1502 b, 1502 c, 1502 d, 1502 e, 1502 f.The distributed filters can include any optical filter described herein,such, for example, an absorptive filter, a refractive filter, adiffractive filter, and/or a reflective filter. The optical filter maybe a color filter (e.g., selecting for a specific range of wavelengths).Examples of absorptive filters include tints, dyes, or stains.Refractive filters include optical elements that filter based ondifferent indices of refraction for different wavelengths of light.Examples of diffractive filters include gratings. Examples of reflectivefilters include dichroic mirrors. The optical filter may include apolarizer. Thus, the waveguides 962 a-968 a (and the waveguides 962b-968 b) can perform color (or subcolor) filtering as described withreference to FIG. 10A. The incoupling optical element 1007 may performless wavelength filtering in such embodiments, because the correspondingwaveguides include a distributed filter that can provide some or all ofthe wavelength filtering.

FIG. 15B shows the waveguide assembly 178 of FIG. 13 with distributedswitches 1506 a, 1506 b, 1506 c, 1506 d, 1506 e, 1506 f. The distributedswitches may include any filter described herein. Distributed switchesmay include an electrically switchable layer and/or an electricallyswitchable volume. Examples of electrically switchable materials includeswitchable dichroics, switchable mirrors, switchable gratings,switchable holograms, switchable glasses, and switchable polarizers. Thedistributed switches may include polymer dispersed liquid crystal orother liquid crystal assemblies (e.g., liquid crystal on silicon(LCoS)). As further described elsewhere herein, the switchable materialcan be switched to alter a reflective, absorptive, refractive,diffractive, and/or polarizing quality of the material. For example, anelectrical signal may cause the material to attenuate (e.g., absorb,deflect away) red light while propagating blue light (e.g., via TIR). Asa further example, a polarizer may be configured to turn on or off basedon an electrical signal. For example, a polarizer may include acholesteric liquid crystal element. Other configurations are alsopossible.

As shown by FIG. 15B, distributed switches 1506 a, 1506 b, 1506 c, 1506d, 1506 e, 1506 f may be disposed along a surface of correspondingwaveguides 962 a, 966 a, 968 a, 962 b, 966 b, 968 b. Such a surface maybe a distal surface from the incoming light 1360 as shown in FIG. 15B,but other surfaces (e.g., a proximal surface to the light 1360, asurface perpendicular to the proximal surface) are also possible. Insome embodiments, the switchable material is disposed throughout thevolume (e.g., volumetrically) of the corresponding waveguides. Aswitchable layer may be disposed within the corresponding waveguidealong a plane that is not parallel to any surface of the waveguide. Forexample, a switchable material may be disposed on a layer not coplanarwith a surface of the waveguide. In some embodiments, the waveguideassembly 178 can include a combination of both distributed filters 1502a-1502 f and distributed switches 1506 a-1506 f.

Waveguide assemblies 178 such as the examples shown in FIGS. 15A and 15Bcan utilize the distributed filters 1502 a-1502 f or the distributedswitches 1506 a-1506 f to perform subcolor filtering within one or morewaveguides 962 a-968 b. In this way, the incoupling optical element 1007may be less wavelength selective than in the waveguide assemblyembodiments 178 that use only one or the other of distributed filteringor distributed switching, which advantageously may reduce degradationalong the optical path that passes through each waveguide in the stack.

Example Color Gamuts

FIG. 16 is an International Commission on Illumination (CIE)chromaticity diagram 1100 with x-y axes (e.g., normalized tristimulusvalues) describing the hypothetical human visual response gamut 1152 atwhich colors are perceived. Each waveguide stack 960 a, 960 b canrepresent colors in a corresponding color gamut, 1160 a, 1160 b, whichis typically smaller than the entire gamut 1152 of all perceivablecolors. The vertices of each gamut 1160 a, 1160 b correspond to thecolors of the corresponding waveguides in each stack. For example, thegamut 1160 a for the waveguide stack 960 a has vertices corresponding tothe colors propagated by the waveguides 962 a, 966 a, and 968 a, and thegamut 1160 b for the waveguide stack 960 b has vertices corresponding tothe colors propagated by the waveguides 962 b, 966 b, and 968 b. Eachgamut 1160 a, 1160 b has an associated white point 1192 a, 1192 b (nearthe center of each gamut) that represents the chromaticity of white.

As can be seen from FIG. 16, the gamuts 1160 a, 1160 b substantiallyoverlap so that each of the waveguide stacks 960 a, 960 b presentssubstantially the same range of colors to the wearer of the display.However, as described above, the corresponding vertices of each gamutare slightly shifted relative to each other, due to the wavelengthmultiplexing. For example, the vertex 1170 a of the gamut 1160 a for thewaveguide stack 960 a may represent green light near 520 nm whereas thevertex 1170 b of the gamut 1160 b for the waveguide stack 960 b mayrepresent green light near 530 nm.

Colors falling within both color gamuts 1160 a, 1160 b can be producedby mixing colors associated with the vertices defining either the firstcolor gamut 1160 a or the second color gamut 1160 b. To produce a givencolor, the proportion that is needed of each vertex wavelength from thefirst color gamut 1160 a may be different from the proportions neededfrom the vertices of the second color gamut 1160 b.

In some embodiments, the wavelengths corresponding to the vertices ofthe color gamuts 1160 a, 1160 b are selected so that the white points1192 a, 1192 b remains substantially the same. For example, the colordifference between the white points 1192 a and 1192 b may be less thanabout the just noticeable difference (JND) in the color space (e.g.,less than about 2.3 in certain CIE color spaces). In other embodiments,the wavelengths corresponding to the vertices can be selected such thatboth color gamuts 1160 a, 1160 b include the white points 1192 a, 1192b. In these embodiments, the wavelengths at the vertices are not fullydetermined by the white points 1192 a, 1192 b.

Although FIG. 16 is shown with two color gamuts 1160 a, 1160 b, this isfor illustrative purposes and is not a limitation. In general the numberof gamuts will be equal to the number of waveguide stacks in thedisplay, and the multiplexing wavelengths of each of the stacks can beselected so that the corresponding white point for each stack issubstantially equal to the white points of the other waveguide stacks.

Example Aspects

In a first Aspect, a waveguide comprising an incoupling optical elementconfigured to couple light into the waveguide, the light comprising afirst wavelength and a second wavelength not equal to the firstwavelength; a light distributing element configured to receive lightfrom the incoupling optical element, the light distributing elementcomprising a wavelength selective region configured to attenuateincoupled light at the second wavelength relative to incoupled light atthe first wavelength; and an outcoupling optical element configured toreceive light from the light distributing element and to couple light atthe first wavelength out of the waveguide.

In a second Aspect, the waveguide of Aspect 1, wherein the incouplingoptical element comprises a grating.

In a third Aspect, the waveguide of any of Aspects 1-2, wherein thewavelength selective region comprises a color filter.

In a fourth Aspect, the waveguide of Aspect 3, wherein the color filtercomprises a dye, a tint, a stain, a dichroic filter, or a Bragg grating.

In a fifth Aspect, the waveguide of any of Aspects 1-4, wherein theincoupling optical element does not comprise a dye, a tint, a stain, adichroic filter, or a Bragg grating.

In a sixth Aspect, the waveguide of any of Aspects 1-5, wherein theoutcoupling optical element does not comprise a dye, a tint, a stain, adichroic filter, or a Bragg grating.

In a seventh Aspect, the waveguide of any of Aspects 1-6, wherein thewavelength selective region comprises an electronically switchableregion.

In an eighth Aspect, the waveguide of any of Aspects 1-7, wherein thewavelength selective region comprises a polymer dispersed liquid crystalgrating.

In a ninth Aspect, the waveguide of any of Aspects 1-8, wherein theincoupling optical element, the light distributing element, or theoutcoupling optical element includes a diffractive optical element.

In a tenth Aspect, the waveguide of Aspect 9, wherein the diffractiveoptical element comprises an analog surface relief grating (ASR), abinary surface relief structure (BSR), a hologram, or a switchablediffractive optical element.

In an eleventh Aspect, a stacked waveguide assembly comprising a firstwaveguide of any of Aspects 1-10, wherein the incoupled light at thesecond wavelength is attenuated relative to the incoupled light at thefirst wavelength; and a second waveguide of any of Aspects 1-10, whereinthe incoupled light at the first wavelength is attenuated relative tothe incoupled light at the second wavelength.

In a twelfth Aspect, a stacked waveguide assembly comprising a firstwaveguide comprising a first incoupling optical element configured toincouple light at a first wavelength and to couple light not at thefirst wavelength out of the first waveguide; a first wavelengthselective region configured to receive incoupled light from the firstincoupling optical element and to propagate the incoupled light to afirst light distributing element, wherein the first wavelength selectiveregion is configured to attenuate the incoupled light not at the firstwavelength relative to incoupled light at the first wavelength, andwherein the first light distributing element is configured to couple theincoupled light at the first wavelength out of the first wavelengthselective region; and a first outcoupling optical element, configured toreceive the incoupled light at the first wavelength from the first lightdistributing element and to couple the incoupled light not at the firstwavelength out of the first waveguide. The stacked waveguide assemblycomprises a second waveguide comprising a second incoupling opticalelement, configured to receive incident light at a second wavelengthdifferent from the first wavelength from the first incoupling opticalelement, to couple incident light not at the second wavelength out ofthe second waveguide, and to incouple the incident light at the secondwavelength; a second wavelength selective region configured to receiveincoupled light from the second incoupling optical element and topropagate the incoupled light to a second light distributing element,wherein the second wavelength selective region is configured toattenuate the incoupled light not at the second wavelength relative toincoupled light at the second wavelength, and wherein the second lightdistributing element is configured to couple the incoupled light at thesecond wavelength out of the second wavelength selective region; and asecond outcoupling optical element, configured to receive the incoupledlight at the second wavelength from the second light distributingelement and to couple the incoupled light not at the second wavelengthout of the second waveguide.

In a thirteenth Aspect, the stacked waveguide assembly of Aspect 12,wherein the incoupling optical element, the light distributing element,or the outcoupling optical element includes a diffractive opticalelement.

In a fourteenth Aspect, the stacked waveguide assembly of Aspect 13,wherein the diffractive optical element comprises an analog surfacerelief grating (ASR), a binary surface relief structure (BSR), ahologram, or a switchable diffractive optical element.

In a fifteenth Aspect, the stacked waveguide assembly of any of Aspects12-14, wherein the wavelength selective region comprises a color filter.

In a sixteenth Aspect, the stacked waveguide assembly of Aspect 15,wherein the color filter comprises a dye, a tint, a stain, a dichroicfilter, or a Bragg grating.

In a seventeenth Aspect, the stacked waveguide assembly of any ofAspects 12-16, wherein the incoupling optical element does not comprisea dye, a tint, a stain, a dichroic filter, or a Bragg grating.

In a eighteenth Aspect, the stacked waveguide assembly of any of Aspects12-17, wherein the outcoupling optical element does not comprise a dye,a tint, a stain, a dichroic filter, or a Bragg grating.

In a nineteenth Aspect, the stacked waveguide assembly of any of Aspects12-18, wherein the wavelength selective region comprises anelectronically switchable region.

In a twentieth Aspect, the stacked waveguide assembly of any of Aspects12-19, wherein the wavelength selective region comprises a polymerdispersed liquid crystal grating.

In a twenty-first Aspect, a method of displaying an optical image, themethod comprising incoupling light having a first wavelength and asecond wavelength different from the first wavelength into a stackedwaveguide assembly comprising a first waveguide and a second waveguide,the first waveguide comprising a first wavelength selective region and afirst outcoupling optical element, and the second waveguide comprising asecond wavelength selective region and a second outcoupling opticalelement; selectively attenuating the incoupled light at the secondwavelength relative to the first wavelength in the first wavelengthselective region; selectively attenuating the incoupled light at thefirst wavelength relative to the first wavelength in the secondwavelength selective region; coupling the incoupled light at the firstwavelength to the first outcoupling optical element; coupling theincoupled light at the first wavelength to the second outcouplingoptical element; and coupling the incoupled light at the firstwavelength and the second wavelength out of the stacked waveguideassembly.

In a twenty-second Aspect, a method of displaying an optical image, themethod comprising incoupling light having a first wavelength and asecond wavelength different from the first wavelength into a waveguide;selectively attenuating the incoupled light at the second wavelengthrelative to the first wavelength in a first wavelength selective region;selectively attenuating the incoupled light at the first wavelengthrelative to the second wavelength in a second wavelength selectiveregion; coupling the incoupled light at the first wavelength from afirst light distributing element to a first outcoupling optical element;coupling the incoupled light at the second wavelength from a secondlight distributing element to a second outcoupling optical element; andcoupling the incoupled light at the first wavelength and secondwavelength out of the outcoupling optical element.

In a twenty-third Aspect, a wearable display system comprising thewaveguide of any of Aspects 1-10 or the stacked waveguide assembly ofany of Aspects 11-20, wherein the wearable display system can be worn bya user.

In a twenty-fourth Aspect, the wearable display system of Aspect 23,wherein the wearable display system can be mounted on the head of theuser.

In a twenty-fifth Aspect, the wearable display system of any of Aspects23-24, wherein the wearable display system is configured to provide anaugmented reality experience for the user.

In a twenty-sixth Aspect, a waveguide comprising an incoupling opticalelement configured to couple light into the waveguide, the lightcomprising a first wavelength and a second wavelength not equal to thefirst wavelength; a light distributing element configured to receivelight from the incoupling optical element and to propagate light viatotal internal reflection, the light distributing element comprising awavelength selective region configured to attenuate incoupled light atthe second wavelength relative to incoupled light at the firstwavelength; and an outcoupling optical element configured to receivelight from the light distributing element and to couple light at thefirst wavelength out of the waveguide.

In a twenty-seventh Aspect, the waveguide of Aspect 26, wherein theincoupling optical element comprises a grating.

In a twenty-eight Aspect, the waveguide of Aspect 26, wherein thewavelength selective region comprises a dye, a tint, a stain, a dichroicfilter, or a Bragg grating.

In a twenty-ninth Aspect, the waveguide of Aspect 26, wherein theincoupling optical element does not comprise a wavelength selectivefilter.

In a thirtieth Aspect, the waveguide of Aspect 26, wherein theoutcoupling optical element does not comprise a wavelength selectivefilter.

In a thirty-first Aspect, the waveguide of Aspect 26, wherein thewavelength selective region comprises an electronically switchableregion.

In a thirty-second Aspect, the waveguide of Aspect 31, furthercomprising a controller configured to switch the electronicallyswitchable region between an on state and an off state.

In a thirty-third Aspect, the waveguide of Aspect 26, wherein thewavelength selective region comprises a polymer dispersed liquid crystalgrating.

In a thirty-fourth Aspect, the waveguide of Aspect 26, wherein the lightdistributing element comprises a diffractive optical element.

In a thirty-fifth Aspect, the waveguide of Aspect 34, wherein thediffractive optical element comprises a grating, a hologram, or aswitchable diffractive optical element.

In a thirty-sixth Aspect, a stacked waveguide assembly comprising afirst waveguide comprising a first layer of an incoupling opticalelement configured to couple light at a first wavelength into a firstlayer of a light distributing element, the light distributing elementcomprising a wavelength selective region; a first layer of thewavelength selective region configured to receive incoupled light fromthe first layer of the incoupling optical element and to attenuate theincoupled light not at the first wavelength relative to incoupled lightat the first wavelength, wherein the first layer of the lightdistributing element is configured to couple the incoupled light at thefirst wavelength out of the first layer of the wavelength selectiveregion; and a first layer of an outcoupling optical element configuredto receive the incoupled light at the first wavelength from the firstlayer of the light distributing element and to couple the incoupledlight out of the first waveguide; and a second waveguide comprising asecond layer of the incoupling optical element configured to couplelight at a second wavelength into a second layer of the lightdistributing element, the second wavelength different from the firstwavelength; a second layer of the wavelength selective region configuredto receive incoupled light from the second layer of the incouplingoptical element and to attenuate the incoupled light not at the secondwavelength relative to incoupled light at the second wavelength, whereinthe second layer of the light distributing element is configured tocouple the incoupled light at the second wavelength out of the secondlayer of the wavelength selective region; and a second layer of theoutcoupling optical element configured to receive the incoupled light atthe second wavelength from the second layer of the light distributingelement and to couple the incoupled light out of the second waveguide.

In a thirty-seventh Aspect, the stacked waveguide assembly of Aspect 36,wherein the first layer of the wavelength selective region comprises afirst color filter and the second layer of the wavelength selectiveregion comprises a second color filter, the first color filterconfigured to attenuate light at the second wavelength, and the secondcolor filter configured to attenuate light at the first wavelength.

In a thirty-eighth Aspect, the stacked waveguide assembly of Aspect 37,wherein the first color filter or the second color filter comprises adye, a tint, a stain, a volumetric optical filter, or a dichroic filter.

In a thirty-ninth Aspect, the stacked waveguide assembly of Aspect 36,wherein the first layer of the wavelength selective region comprises afirst electronically switchable region, and the second layer of thewavelength selective region comprises a second electronically switchableregion.

In a fortieth Aspect, the stacked waveguide assembly of Aspect 39,further comprising a controller configured to electronically control thefirst electronically switchable region and the second electronicallyswitchable region to modulate light in the stacked waveguide assembly.

In a forty-first Aspect, the stacked waveguide assembly of Aspect 40,wherein the controller is configured to switch the first electronicallyswitchable region to modulate light in the first layer of the lightdistributing element and to switch the second electronically switchableregion to not modulate light in the second layer of the lightdistributing element.

In a forty-second Aspect, the stacked waveguide assembly of Aspect 40,wherein the controller is configured to electronically control the firstelectronically switchable region and the second electronicallyswitchable region to steer the incoupled light to expand a field ofview.

In a forty-third Aspect, the stacked waveguide assembly of Aspect 36,wherein the first layer of the wavelength selective region is configuredto alter an index of refraction of light not at the first wavelength orthe second layer of the wavelength selective region is configured toalter an index of refraction of light not at the second wavelength.

In a forty-fourth Aspect, the stacked waveguide assembly of Aspect 36,wherein the first layer or the second layer of the wavelength selectiveregion comprises a polarizer.

In a forty-fifth Aspect, the stacked waveguide assembly of Aspect 36,wherein the first wavelength is associated with a first subcolor of acolor and the second wavelength is associated with a second subcolor ofthe color, the second subcolor different from the first subcolor.

In a forty-sixth Aspect, a display comprising a first waveguide stackcomprising a first plurality of waveguides, the first plurality ofwaveguides comprising a first waveguide configured to propagate light ata first subcolor of a color; a second waveguide stack comprising asecond plurality of waveguides, the second plurality of waveguidescomprising a second waveguide configured to propagate light at a secondsubcolor of the color different from the first subcolor; and anincoupling optical system configured to incouple light into the firstwaveguide stack and the second waveguide stack, the incoupling opticalsystem comprising a first incoupling optical element configured tocouple light at the first subcolor into the first waveguide; and asecond incoupling portion configured to couple light at the secondsubcolor into the second waveguide.

In a forty-seventh Aspect, the display of Aspect 46, wherein the firstwaveguide stack comprises an outcoupling optical element configured tocouple light out of the first waveguide stack.

In a forty-eighth Aspect, the display of Aspect 47, wherein theincoupling optical element comprises a diffractive optical element.

In a forty-ninth Aspect, the display of Aspect 48, wherein thediffractive optical element comprises a hologram.

In a fiftieth Aspect, the display of Aspect 46, wherein the waveguideassembly further comprises a preliminary light filter system.

In a fifty-first Aspect, the display of Aspect 50, wherein thepreliminary light filter system comprises a grating.

In a fifty-second Aspect, the display of Aspect 46, wherein the firstincoupling optical element is configured to transmit light having a peakwavelength different from a peak wavelength of the first subcolor byless than 120 nm.

In a fifty-third Aspect, the display of Aspect 46, wherein the firstincoupling optical element is configured to transmit light having awidth of a wavelength distribution not greater than about 5-55 nm.

In a fifty-fourth Aspect, the display of Aspects 46, wherein the firstincoupling optical element is configured to transmit light having awidth of a wavelength distribution profile not greater than about 220nm.

In a fifty-fifth Aspect, a waveguide assembly comprising a light sourcethat emits light at a plurality of subcolors of a color; and a firstwaveguide stack configured to incouple light at a first color of thefirst wavelength and a first color of the second wavelength, the firstwaveguide stack comprising a first plurality of waveguides, the firstplurality of waveguides comprising a first waveguide configured topropagate light at a first subcolor of a color; a second plurality ofwaveguides, the second plurality of waveguides comprising a secondwaveguide configured to propagate light at a second subcolor of thecolor different from the first subcolor; and an incoupling opticalsystem configured to incouple light into the first waveguide stack andthe second waveguide stack.

In a fifty-sixth Aspect, a waveguide assembly comprising a firstwaveguide stack configured to receive light at first and secondsubcolors, wherein the first and second subcolors are not subcolors ofthe same color, the first waveguide stack comprising a first waveguidecomprising a first grating system configured to incouple light at thefirst subcolor; and a second waveguide comprising a second gratingsystem, the second waveguide configured to incouple light at the secondsubcolor, and a second waveguide stack configured to receive light atthird and fourth subcolors, wherein the third and fourth subcolors arenot subcolors of the same color, the second waveguide stack comprising athird waveguide comprising a third grating system configured to incouplelight at the third subcolor; and a fourth waveguide comprising a fourthgrating system, the fourth waveguide configured to incouple light at thefourth subcolor.

In a fifty-seventh Aspect, the waveguide assembly of Aspect 56, whereinthe first waveguide stack comprises an incoupling optical element.

In a fifty-eighth Aspect, the waveguide assembly of Aspect 57, whereinthe light distributing element comprises a diffractive optical element.

In a fifty-ninth Aspect, the waveguide assembly of Aspect 58, whereinthe diffractive optical element comprises a grating.

In a sixtieth Aspect, the waveguide assembly of any of Aspects 46-59,wherein the waveguide assembly further comprises a preliminary lightfilter system comprising a reflective optical element.

In a sixty-first Aspect, a wavelength multiplexing assembly comprising alight source that emits a plurality of subcolors at a first wavelengthand a plurality of subcolors at a second wavelength; a first waveguidestack configured to incouple light at a first subcolor of the firstwavelength and at a first subcolor of the second wavelength, the firstwaveguide stack comprising a first waveguide configured to incouplelight at the first subcolor of the first wavelength; and a secondwaveguide configured to incouple light at the second subcolor of thefirst wavelength; and a second waveguide stack configured to incouplelight at a second subcolor of the first wavelength and at a secondsubcolor of the second wavelength, the first waveguide stack comprisinga third waveguide configured to incouple light at the second subcolor ofthe first wavelength; and a fourth waveguide configured to incouplelight at the second subcolor of the second wavelength.

In a sixty-second Aspect, the wavelength multiplexing assembly of Aspect61, wherein the first waveguide, the second waveguide, the thirdwaveguide, or the fourth waveguide comprises an incoupling opticalelement, a light distributing element, or an outcoupling opticalelement.

In a sixty-third Aspect, the wavelength multiplexing assembly of Aspect62, wherein the incoupling optical element, the light distributingelement, or the outcoupling optical element comprises a diffractiveoptical element.

In a sixty-fourth Aspect, the wavelength multiplexing assembly of Aspect63, wherein the diffractive optical element comprises a switchablediffractive optical element.

In a sixty-fifth Aspect, the wavelength multiplexing assembly of Aspect64, wherein the waveguide assembly further comprises a preliminary lightfilter system comprising a refractive optical element.

CONCLUSION

Each of the processes, methods, and algorithms described herein and/ordepicted in the attached figures may be embodied in, and fully orpartially automated by, code modules executed by one or more physicalcomputing systems, hardware computer processors, application-specificcircuitry, and/or electronic hardware configured to execute specific andparticular computer instructions. For example, computing systems caninclude general purpose computers (e.g., servers) programmed withspecific computer instructions or special purpose computers, specialpurpose circuitry, and so forth. A code module may be compiled andlinked into an executable program, installed in a dynamic link library,or may be written in an interpreted programming language. In someimplementations, particular operations and methods may be performed bycircuitry that is specific to a given function.

Further, certain implementations of the functionality of the presentdisclosure are sufficiently mathematically, computationally, ortechnically complex that application-specific hardware or one or morephysical computing devices (utilizing appropriate specialized executableinstructions) may be necessary to perform the functionality, forexample, due to the volume or complexity of the calculations involved orto provide results substantially in real-time. For example, a video mayinclude many frames, with each frame having millions of pixels, andspecifically programmed computer hardware is necessary to process thevideo data to provide a desired image processing task or application ina commercially reasonable amount of time. As another example, theeye-tracking calculations and the application of the appropriateeye-pose-dependent display calibration in real-time typically isperformed by application-specific hardware or physical computing devicesprogrammed with specific computer-executable instructions.

Code modules or any type of data may be stored on any type ofnon-transitory computer-readable medium, such as physical computerstorage including hard drives, solid state memory, random access memory(RAM), read only memory (ROM), optical disc, volatile or non-volatilestorage, combinations of the same and/or the like. The methods andmodules (or data) may also be transmitted as generated data signals(e.g., as part of a carrier wave or other analog or digital propagatedsignal) on a variety of computer-readable transmission mediums,including wireless-based and wired/cable-based mediums, and may take avariety of forms (e.g., as part of a single or multiplexed analogsignal, or as multiple discrete digital packets or frames). The resultsof the disclosed processes or process steps may be stored, persistentlyor otherwise, in any type of non-transitory, tangible computer storageor may be communicated via a computer-readable transmission medium.

Any processes, blocks, states, steps, or functionalities in flowdiagrams described herein and/or depicted in the attached figures shouldbe understood as potentially representing code modules, segments, orportions of code which include one or more executable instructions forimplementing specific functions (e.g., logical or arithmetical) or stepsin the process. The various processes, blocks, states, steps, orfunctionalities can be combined, rearranged, added to, deleted from,modified, or otherwise changed from the illustrative examples providedherein. In some embodiments, additional or different computing systemsor code modules may perform some or all of the functionalities describedherein. The methods and processes described herein are also not limitedto any particular sequence, and the blocks, steps, or states relatingthereto can be performed in other sequences that are appropriate, forexample, in serial, in parallel, or in some other manner. Tasks orevents may be added to or removed from the disclosed exampleembodiments. Moreover, the separation of various system components inthe implementations described herein is for illustrative purposes andshould not be understood as requiring such separation in allimplementations. It should be understood that the described programcomponents, methods, and systems can generally be integrated together ina single computer product or packaged into multiple computer products.Many implementation variations are possible.

The processes, methods, and systems may be implemented in a network (ordistributed) computing environment. Network environments includeenterprise-wide computer networks, intranets, local area networks (LAN),wide area networks (WAN), personal area networks (PAN), cloud computingnetworks, crowd-sourced computing networks, the Internet, and the WorldWide Web. The network may be a wired or a wireless network or any othertype of communication network.

The systems and methods of the disclosure each have several innovativeaspects, no single one of which is solely responsible or required forthe desirable attributes disclosed herein. The various features andprocesses described above may be used independently of one another, ormay be combined in various ways. All possible combinations andsubcombinations are intended to fall within the scope of thisdisclosure. Various modifications to the implementations described inthis disclosure may be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to otherimplementations without departing from the spirit or scope of thisdisclosure. Thus, the claims are not intended to be limited to theimplementations shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

Certain features that are described in this specification in the contextof separate implementations also can be implemented in combination in asingle implementation. Conversely, various features that are describedin the context of a single implementation also can be implemented inmultiple implementations separately or in any suitable subcombination.Moreover, although features may be described above as acting in certaincombinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claimed combination may be directed to asubcombination or variation of a subcombination. No single feature orgroup of features is necessary or indispensable to each and everyembodiment.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and/orsteps. Thus, such conditional language is not generally intended toimply that features, elements and/or steps are in any way required forone or more embodiments or that one or more embodiments necessarilyinclude logic for deciding, with or without author input or prompting,whether these features, elements and/or steps are included or are to beperformed in any particular embodiment. The terms “comprising,”“including,” “having,” and the like are synonymous and are usedinclusively, in an open-ended fashion, and do not exclude additionalelements, features, acts, operations, and so forth. Also, the term “or”is used in its inclusive sense (and not in its exclusive sense) so thatwhen used, for example, to connect a list of elements, the term “or”means one, some, or all of the elements in the list. In addition, thearticles “a,” “an,” and “the” as used in this application and theappended claims are to be construed to mean “one or more” or “at leastone” unless specified otherwise.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: A, B, or C” is intended to cover: A, B, C,A and B, A and C, B and C, and A, B, and C. Conjunctive language such asthe phrase “at least one of X, Y and Z,” unless specifically statedotherwise, is otherwise understood with the context as used in generalto convey that an item, term, etc. may be at least one of X, Y or Z.Thus, such conjunctive language is not generally intended to imply thatcertain embodiments require at least one of X, at least one of Y and atleast one of Z to each be present.

Similarly, while operations may be depicted in the drawings in aparticular order, it is to be recognized that such operations need notbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Further, the drawings may schematically depict one more exampleprocesses in the form of a flowchart. However, other operations that arenot depicted can be incorporated in the example methods and processesthat are schematically illustrated. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the illustrated operations. Additionally, the operations may berearranged or reordered in other implementations. In certaincircumstances, multitasking and parallel processing may be advantageous.Moreover, the separation of various system components in theimplementations described above should not be understood as requiringsuch separation in all implementations, and it should be understood thatthe described program components and systems can generally be integratedtogether in a single software product or packaged into multiple softwareproducts. Additionally, other implementations are within the scope ofthe following claims. In some cases, the actions recited in the claimscan be performed in a different order and still achieve desirableresults.

What is claimed is:
 1. A display comprising: a first waveguide stackcomprising a first plurality of waveguides, the first plurality ofwaveguides comprising a first waveguide configured to propagate light ata first subcolor of a color; a second waveguide stack comprising asecond plurality of waveguides, the second plurality of waveguidescomprising a second waveguide configured to propagate light at a secondsubcolor of the color different from the first subcolor; and anincoupling optical system configured to incouple light into the firstwaveguide stack and the second waveguide stack, the incoupling opticalsystem comprising: a first incoupling optical element configured tocouple light at the first subcolor into the first waveguide; and asecond incoupling optical element configured to couple light at thesecond subcolor into the second waveguide.
 2. The display of claim 1,wherein the first waveguide stack comprises an outcoupling opticalelement configured to couple light out of the first waveguide stack. 3.The display of claim 2, wherein the first incoupling optical element orthe second incoupling optical element comprises a diffractive opticalelement.
 4. The display of claim 3, wherein the diffractive opticalelement comprises a hologram.
 5. The display of claim 1, wherein thewaveguide stack further comprises a preliminary light filter system. 6.The display of claim 5, wherein the preliminary light filter systemcomprises a grating.
 7. The display of claim 1, wherein the firstincoupling optical element is configured to transmit light having a peakwavelength different from a peak wavelength of the first subcolor byless than 120 nm.
 8. The display of claim 1, wherein the firstincoupling optical element is configured to transmit light having awidth of a wavelength distribution not greater than about 5-55 nm. 9.The display of claim 1, wherein the first incoupling optical element isconfigured to transmit light having a width of a wavelength distributionprofile not greater than about 220 nm.
 10. A waveguide assemblycomprising: a first waveguide stack configured to receive light at firstand second subcolors, wherein the first and second subcolors are notsubcolors of the same color, the first waveguide stack comprising: afirst waveguide comprising a first grating system configured to incouplelight at the first subcolor; and a second waveguide comprising a secondgrating system, the second waveguide configured to incouple light at thesecond subcolor, and a second waveguide stack configured to receivelight at third and fourth subcolors, wherein the third and fourthsubcolors are not subcolors of the same color, the second waveguidestack comprising: a third waveguide comprising a third grating systemconfigured to incouple light at the third subcolor; and a fourthwaveguide comprising a fourth grating system, the fourth waveguideconfigured to incouple light at the fourth subcolor.
 11. The waveguideassembly of claim 11, wherein the first waveguide stack or the secondwaveguide stack comprises an incoupling optical element.
 12. Thewaveguide assembly of claim 12, wherein the incoupling optical elementcomprises a diffractive optical element.
 13. The waveguide assembly ofclaim 13, wherein the diffractive optical element comprises a grating.14. The waveguide assembly of claim 11, further comprising a preliminarylight filter system comprising a reflective optical element.
 15. Thewaveguide assembly of claim 11, further comprising a light sourceconfigured to emit light at light at the first, the second, the third,and the fourth subcolors.
 16. A wavelength multiplexing assemblycomprising: a light source that emits a plurality of subcolors at afirst wavelength and a plurality of subcolors at a second wavelength; afirst waveguide stack configured to incouple light at a first subcolorof the first wavelength and at a first subcolor of the secondwavelength, the first waveguide stack comprising: a first waveguideconfigured to incouple light at the first subcolor of the firstwavelength; and a second waveguide configured to incouple light at thesecond subcolor of the first wavelength; and a second waveguide stackconfigured to incouple light at a second subcolor of the firstwavelength and at a second subcolor of the second wavelength, the firstwaveguide stack comprising: a third waveguide configured to incouplelight at the second subcolor of the first wavelength; and a fourthwaveguide configured to incouple light at the second subcolor of thesecond wavelength.
 17. The wavelength multiplexing assembly of claim 16,wherein the first waveguide, the second waveguide, the third waveguide,or the fourth waveguide comprises an incoupling optical element, a lightdistributing element, or an outcoupling optical element.
 18. Thewavelength multiplexing assembly of claim 17, wherein the incouplingoptical element, the light distributing element, or the outcouplingoptical element comprises a diffractive optical element.
 19. Thewavelength multiplexing assembly of claim 18, wherein the diffractiveoptical element comprises a switchable diffractive optical element. 20.The wavelength multiplexing assembly of claim 16, wherein the waveguideassembly further comprises a preliminary light filter system comprisinga refractive optical element.